diff --git a/.github/workflows/build-test.yml b/.github/workflows/build-test.yml
index d6e08261..31727184 100644
--- a/.github/workflows/build-test.yml
+++ b/.github/workflows/build-test.yml
@@ -59,8 +59,17 @@ jobs:
         run: yarn test:unit
 
   test-integration:
-    name: Test (Integration)
+    name: Test (Integration) - ${{ matrix.config.name }}
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        config:
+          - name: Custom gas token with 18 decimals
+            args: --tokenbridge --l3node --l3-token-bridge --l3-fee-token
+            decimals: 18
+          - name: Custom gas token with 6 decimals
+            args: --tokenbridge --l3node --l3-token-bridge --l3-fee-token --l3-fee-token-decimals 6
+            decimals: 6
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -72,7 +81,7 @@ jobs:
         uses: OffchainLabs/actions/run-nitro-test-node@feat-simplify
         with:
           nitro-testnode-ref: release
-          args: --tokenbridge --l3node --l3-token-bridge --l3-fee-token
+          args: ${{ matrix.config.args }}
 
       - name: Copy .env
         run: cp ./.env.example ./.env
@@ -81,4 +90,4 @@ jobs:
         run: yarn build
 
       - name: Test
-        run: yarn test:integration
+        run: DECIMALS=${{matrix.config.decimals}} yarn test:integration
diff --git a/src/chains.ts b/src/chains.ts
index 04dc167c..89e307c6 100644
--- a/src/chains.ts
+++ b/src/chains.ts
@@ -125,13 +125,16 @@ export function registerCustomParentChain(
   customParentChains[chain.id] = chain;
 }
 
-export const chains = [
+export const mainnets = [
   // mainnet L1
   mainnet,
   // mainnet L2
   arbitrumOne,
   arbitrumNova,
   base,
+];
+
+export const testnets = [
   // testnet L1
   sepolia,
   holesky,
@@ -142,7 +145,9 @@ export const chains = [
   nitroTestnodeL1,
   nitroTestnodeL2,
   nitroTestnodeL3,
-] as const;
+];
+
+export const chains = [...mainnets, ...testnets] as const;
 
 export {
   // mainnet L1
diff --git a/src/createRollup.integration.test.ts b/src/createRollup.integration.test.ts
index 278c9a5f..98114faf 100644
--- a/src/createRollup.integration.test.ts
+++ b/src/createRollup.integration.test.ts
@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { Address, createPublicClient, http, parseGwei, zeroAddress } from 'viem';
+import { createPublicClient, http, parseGwei, zeroAddress } from 'viem';
 
 import { nitroTestnodeL2 } from './chains';
 import {
diff --git a/src/createRollupEnoughCustomFeeTokenAllowance.ts b/src/createRollupEnoughCustomFeeTokenAllowance.ts
index e7cbfa23..735fd3ad 100644
--- a/src/createRollupEnoughCustomFeeTokenAllowance.ts
+++ b/src/createRollupEnoughCustomFeeTokenAllowance.ts
@@ -1,11 +1,12 @@
 import { Address, PublicClient, Transport, Chain } from 'viem';
 
-import { fetchAllowance } from './utils/erc20';
+import { fetchAllowance, fetchDecimals } from './utils/erc20';
 import { getRollupCreatorAddress } from './utils/getRollupCreatorAddress';
 
 import { Prettify } from './types/utils';
 import { WithRollupCreatorAddressOverride } from './types/createRollupTypes';
 import { createRollupGetRetryablesFeesWithDefaults } from './createRollupGetRetryablesFees';
+import { scaleToNativeTokenDecimals } from './utils/decimals';
 
 export type CreateRollupEnoughCustomFeeTokenAllowanceParams<TChain extends Chain | undefined> =
   Prettify<
@@ -37,5 +38,10 @@ export async function createRollupEnoughCustomFeeTokenAllowance<TChain extends C
     maxFeePerGasForRetryables,
   });
 
-  return allowance >= fees;
+  const decimals = await fetchDecimals({
+    address: nativeToken,
+    publicClient,
+  });
+
+  return allowance >= scaleToNativeTokenDecimals({ amount: fees, decimals });
 }
diff --git a/src/createRollupGetRetryablesFees.ts b/src/createRollupGetRetryablesFees.ts
index 4b73e562..0ebf2148 100644
--- a/src/createRollupGetRetryablesFees.ts
+++ b/src/createRollupGetRetryablesFees.ts
@@ -7,6 +7,7 @@ import {
   EstimateGasParameters,
   encodeFunctionData,
   decodeFunctionResult,
+  parseEther,
 } from 'viem';
 
 import { rollupCreatorABI } from './contracts/RollupCreator';
@@ -104,9 +105,8 @@ export async function createRollupGetRetryablesFees<TChain extends Chain | undef
 
   const baseFeeWithBuffer = applyPercentIncrease({
     base: await publicClient.getGasPrice(),
-    // for custom gas token chains, retryable fees don't scale with parent base fee, so there's no need for any buffer
-    // for eth chains, add 30% buffer in case of a spike
-    percentIncrease: isCustomGasToken ? undefined : 30n,
+    // add 30% buffer in case of a spike
+    percentIncrease: 30n,
   });
 
   const callParams: CallParameters = {
@@ -140,8 +140,14 @@ export async function createRollupGetRetryablesFees<TChain extends Chain | undef
   });
 
   return isCustomGasToken
-    ? // for custom gas token chains, retryable fees don't scale with parent base fee, so there's no need for any buffer
-      decodedResult
+    ? // for custom gas token chains, retryable fees don't scale with parent base fee and are constant at 124708400000000000
+      //
+      // we add some buffer (around 100k gwei) due to potential rounding issues for non-18 decimals, because:
+      // - in the sdk, we get the total cost, then scale and round up
+      // - in the contract, we scale and round up each component, then add them together, which can lead to a very tiny discrepancy
+      //
+      // https://github.com/OffchainLabs/nitro-contracts/blob/main/src/rollup/RollupCreator.sol#L287-L302
+      parseEther('0.1248')
     : // for eth chains, add 3% buffer
       applyPercentIncrease({ base: decodedResult, percentIncrease: 3n });
 }
diff --git a/src/createRollupGetRetryablesFees.unit.test.ts b/src/createRollupGetRetryablesFees.unit.test.ts
index 59f9f3f9..720ae720 100644
--- a/src/createRollupGetRetryablesFees.unit.test.ts
+++ b/src/createRollupGetRetryablesFees.unit.test.ts
@@ -22,10 +22,10 @@ it('successfully fetches retryable fees for an eth-based chain', async () => {
 it('successfully fetches retryable fees for a custom gas token chain', async () => {
   const fees = await createRollupGetRetryablesFees(sepoliaClient, {
     account: '0x38f918D0E9F1b721EDaA41302E399fa1B79333a9',
-    nativeToken: '0xaf88d065e77c8cc2239327c5edb3a432268e5831',
+    nativeToken: '0x0625afb445c3b6b7b929342a04a22599fd5dbb59',
     maxFeePerGasForRetryables: parseGwei('0.1'),
   });
 
   expect(fees).toBeTypeOf('bigint');
-  expect(fees).toEqual(124708400000000000n);
+  expect(fees).toEqual(124800000000000000n);
 });
diff --git a/src/createRollupPrepareCustomFeeTokenApprovalTransactionRequest.ts b/src/createRollupPrepareCustomFeeTokenApprovalTransactionRequest.ts
index 989698e7..e3695e9f 100644
--- a/src/createRollupPrepareCustomFeeTokenApprovalTransactionRequest.ts
+++ b/src/createRollupPrepareCustomFeeTokenApprovalTransactionRequest.ts
@@ -1,13 +1,13 @@
 import { Address, PublicClient, Transport, Chain } from 'viem';
 
-import { approvePrepareTransactionRequest } from './utils/erc20';
+import { approvePrepareTransactionRequest, fetchDecimals } from './utils/erc20';
 import { validateParentChain } from './types/ParentChain';
 import { getRollupCreatorAddress } from './utils/getRollupCreatorAddress';
 
 import { Prettify } from './types/utils';
 import { WithRollupCreatorAddressOverride } from './types/createRollupTypes';
 import { createRollupGetRetryablesFeesWithDefaults } from './createRollupGetRetryablesFees';
-import { applyPercentIncrease } from './utils/gasOverrides';
+import { scaleToNativeTokenDecimals } from './utils/decimals';
 
 export type CreateRollupPrepareCustomFeeTokenApprovalTransactionRequestParams<
   TChain extends Chain | undefined,
@@ -39,11 +39,16 @@ export async function createRollupPrepareCustomFeeTokenApprovalTransactionReques
     maxFeePerGasForRetryables,
   });
 
+  const decimals = await fetchDecimals({
+    address: nativeToken,
+    publicClient,
+  });
+
   const request = await approvePrepareTransactionRequest({
     address: nativeToken,
     owner: account,
     spender: rollupCreatorAddressOverride ?? getRollupCreatorAddress(publicClient),
-    amount: amount ?? fees,
+    amount: amount ?? scaleToNativeTokenDecimals({ amount: fees, decimals }),
     publicClient,
   });
 
diff --git a/src/createRollupPrepareTransactionRequest.ts b/src/createRollupPrepareTransactionRequest.ts
index e86846d1..0fbf4d7b 100644
--- a/src/createRollupPrepareTransactionRequest.ts
+++ b/src/createRollupPrepareTransactionRequest.ts
@@ -68,10 +68,9 @@ export async function createRollupPrepareTransactionRequest<TChain extends Chain
       );
     }
 
-    // custom fee token is only allowed to have 18 decimals
-    if ((await fetchDecimals({ address: params.nativeToken, publicClient })) !== 18) {
+    if ((await fetchDecimals({ address: params.nativeToken, publicClient })) > 36) {
       throw new Error(
-        `"params.nativeToken" can only be configured with a token that uses 18 decimals.`,
+        `"params.nativeToken" can only be configured with a token that uses 36 decimals or less.`,
       );
     }
   }
diff --git a/src/createRollupPrepareTransactionRequest.unit.test.ts b/src/createRollupPrepareTransactionRequest.unit.test.ts
index 8db6405e..81871239 100644
--- a/src/createRollupPrepareTransactionRequest.unit.test.ts
+++ b/src/createRollupPrepareTransactionRequest.unit.test.ts
@@ -262,38 +262,6 @@ it(`fails to prepare transaction request if ArbOS version is incompatible with C
   );
 });
 
-it(`fails to prepare transaction request if "params.nativeToken" doesn't use 18 decimals`, async () => {
-  // generate a random chain id
-  const chainId = generateChainId();
-
-  // create the chain config
-  const chainConfig = prepareChainConfig({
-    chainId,
-    arbitrum: { InitialChainOwner: deployer.address, DataAvailabilityCommittee: true },
-  });
-
-  // prepare the transaction for deploying the core contracts
-  await expect(
-    createRollupPrepareTransactionRequest({
-      params: {
-        config: createRollupPrepareDeploymentParamsConfig(publicClient, {
-          chainId: BigInt(chainId),
-          owner: deployer.address,
-          chainConfig,
-        }),
-        batchPosters: [deployer.address],
-        validators: [deployer.address],
-        // USDC on Arbitrum Sepolia has 6 decimals
-        nativeToken: '0x75faf114eafb1BDbe2F0316DF893fd58CE46AA4d',
-      },
-      account: deployer.address,
-      publicClient,
-    }),
-  ).rejects.toThrowError(
-    `"params.nativeToken" can only be configured with a token that uses 18 decimals.`,
-  );
-});
-
 it(`fails to prepare transaction request if "params.maxDataSize" is not provided for a custom parent chain`, async () => {
   // generate a random chain id
   const chainId = generateChainId();
@@ -458,3 +426,37 @@ it(`successfully prepares a transaction request with a custom parent chain`, asy
   expect(txRequest.chainId).toEqual(chainId);
   expect(txRequest.gas).toEqual(1_000n);
 });
+
+it(`successfully prepare transaction request if "params.nativeToken" uses supported number of decimals`, async () => {
+  // generate a random chain id
+  const chainId = generateChainId();
+
+  // create the chain config
+  const chainConfig = prepareChainConfig({
+    chainId,
+    arbitrum: { InitialChainOwner: deployer.address, DataAvailabilityCommittee: true },
+  });
+
+  const txRequest = await createRollupPrepareTransactionRequest({
+    params: {
+      config: createRollupPrepareDeploymentParamsConfig(publicClient, {
+        chainId: BigInt(chainId),
+        owner: deployer.address,
+        chainConfig,
+      }),
+      batchPosters: [deployer.address],
+      validators: [deployer.address],
+      nativeToken: '0x75faf114eafb1BDbe2F0316DF893fd58CE46AA4d', // USDC
+    },
+    value: createRollupDefaultRetryablesFees,
+    account: deployer.address,
+    publicClient,
+    gasOverrides: { gasLimit: { base: 1_000n } },
+  });
+
+  expect(txRequest.account).toEqual(deployer.address);
+  expect(txRequest.from).toEqual(deployer.address);
+  expect(txRequest.to).toEqual(rollupCreatorAddress[arbitrumSepolia.id]);
+  expect(txRequest.chainId).toEqual(arbitrumSepolia.id);
+  expect(txRequest.gas).toEqual(1_000n);
+});
diff --git a/src/createTokenBridge.integration.test.ts b/src/createTokenBridge.integration.test.ts
index 83d870dc..66dc038a 100644
--- a/src/createTokenBridge.integration.test.ts
+++ b/src/createTokenBridge.integration.test.ts
@@ -20,6 +20,7 @@ import { createTokenBridgePrepareSetWethGatewayTransactionRequest } from './crea
 import { createTokenBridgePrepareSetWethGatewayTransactionReceipt } from './createTokenBridgePrepareSetWethGatewayTransactionReceipt';
 import { createTokenBridge } from './createTokenBridge';
 import { TokenBridgeContracts } from './types/TokenBridgeContracts';
+import { scaleToNativeTokenDecimals } from './utils/decimals';
 
 const testnodeAccounts = getNitroTestnodePrivateKeyAccounts();
 const l2RollupOwner = testnodeAccounts.l2RollupOwner;
@@ -104,6 +105,8 @@ async function checkWethGateways(
   expect(tokenBridgeContracts.orbitChainContracts.wethGateway).not.toEqual(zeroAddress);
 }
 
+const nativeTokenDecimals = process.env.DECIMALS ? Number(process.env.DECIMALS) : 18;
+
 describe('createTokenBridge utils function', () => {
   it(`successfully deploys token bridge contracts through token bridge creator`, async () => {
     const testnodeInformation = getInformationFromTestnode();
@@ -218,7 +221,10 @@ describe('createTokenBridge utils function', () => {
       data: encodeFunctionData({
         abi: erc20ABI,
         functionName: 'transfer',
-        args: [l3RollupOwner.address, parseEther('500')],
+        args: [
+          l3RollupOwner.address,
+          scaleToNativeTokenDecimals({ amount: 500n, decimals: nativeTokenDecimals }),
+        ],
       }),
       value: BigInt(0),
       account: l3TokenBridgeDeployer,
@@ -384,7 +390,10 @@ describe('createTokenBridge', () => {
       data: encodeFunctionData({
         abi: erc20ABI,
         functionName: 'transfer',
-        args: [l3RollupOwner.address, parseEther('500')],
+        args: [
+          l3RollupOwner.address,
+          scaleToNativeTokenDecimals({ amount: 500n, decimals: nativeTokenDecimals }),
+        ],
       }),
       value: BigInt(0),
       account: l3TokenBridgeDeployer,
diff --git a/src/createTokenBridgeEnoughCustomFeeTokenAllowance.ts b/src/createTokenBridgeEnoughCustomFeeTokenAllowance.ts
index 1d4fbb87..29b6b816 100644
--- a/src/createTokenBridgeEnoughCustomFeeTokenAllowance.ts
+++ b/src/createTokenBridgeEnoughCustomFeeTokenAllowance.ts
@@ -1,11 +1,12 @@
 import { Address, PublicClient, Transport, Chain } from 'viem';
 
-import { fetchAllowance } from './utils/erc20';
+import { fetchAllowance, fetchDecimals } from './utils/erc20';
 import { createTokenBridgeDefaultRetryablesFees } from './constants';
 
 import { Prettify } from './types/utils';
 import { WithTokenBridgeCreatorAddressOverride } from './types/createTokenBridgeTypes';
 import { getTokenBridgeCreatorAddress } from './utils/getTokenBridgeCreatorAddress';
+import { scaleToNativeTokenDecimals } from './utils/decimals';
 
 export type CreateTokenBridgeEnoughCustomFeeTokenAllowanceParams<TChain extends Chain | undefined> =
   Prettify<
@@ -31,5 +32,16 @@ export async function createTokenBridgeEnoughCustomFeeTokenAllowance<
     publicClient,
   });
 
-  return allowance >= createTokenBridgeDefaultRetryablesFees;
+  const decimals = await fetchDecimals({
+    address: nativeToken,
+    publicClient,
+  });
+
+  return (
+    allowance >=
+    scaleToNativeTokenDecimals({
+      amount: createTokenBridgeDefaultRetryablesFees,
+      decimals,
+    })
+  );
 }
diff --git a/src/createTokenBridgePrepareCustomFeeTokenApprovalTransactionRequest.ts b/src/createTokenBridgePrepareCustomFeeTokenApprovalTransactionRequest.ts
index 11614683..a439bbe9 100644
--- a/src/createTokenBridgePrepareCustomFeeTokenApprovalTransactionRequest.ts
+++ b/src/createTokenBridgePrepareCustomFeeTokenApprovalTransactionRequest.ts
@@ -1,12 +1,13 @@
 import { Address, PublicClient, Transport, Chain, maxInt256 } from 'viem';
 
-import { approvePrepareTransactionRequest } from './utils/erc20';
+import { approvePrepareTransactionRequest, fetchDecimals } from './utils/erc20';
 
 import { Prettify } from './types/utils';
 import { validateParentChain } from './types/ParentChain';
 import { WithTokenBridgeCreatorAddressOverride } from './types/createTokenBridgeTypes';
 import { getTokenBridgeCreatorAddress } from './utils/getTokenBridgeCreatorAddress';
 import { createTokenBridgeDefaultRetryablesFees } from './constants';
+import { scaleToNativeTokenDecimals } from './utils/decimals';
 
 export type CreateTokenBridgePrepareCustomFeeTokenApprovalTransactionRequestParams<
   TChain extends Chain | undefined,
@@ -30,11 +31,21 @@ export async function createTokenBridgePrepareCustomFeeTokenApprovalTransactionR
 }: CreateTokenBridgePrepareCustomFeeTokenApprovalTransactionRequestParams<TChain>) {
   const { chainId } = validateParentChain(publicClient);
 
+  const decimals = await fetchDecimals({
+    address: nativeToken,
+    publicClient,
+  });
+
   const request = await approvePrepareTransactionRequest({
     address: nativeToken,
     owner,
     spender: tokenBridgeCreatorAddressOverride ?? getTokenBridgeCreatorAddress(publicClient),
-    amount: amount ?? createTokenBridgeDefaultRetryablesFees,
+    amount:
+      amount ??
+      scaleToNativeTokenDecimals({
+        amount: createTokenBridgeDefaultRetryablesFees,
+        decimals,
+      }),
     publicClient,
   });
 
diff --git a/src/decorators/arbOwnerPublicActionsUpgradeExecutor.integration.test.ts b/src/decorators/arbOwnerPublicActionsUpgradeExecutor.integration.test.ts
index d4558ec6..1ec887e3 100644
--- a/src/decorators/arbOwnerPublicActionsUpgradeExecutor.integration.test.ts
+++ b/src/decorators/arbOwnerPublicActionsUpgradeExecutor.integration.test.ts
@@ -1,5 +1,5 @@
 import { it, expect } from 'vitest';
-import { Address, createPublicClient, http, parseGwei, Client } from 'viem';
+import { Address, createPublicClient, http } from 'viem';
 import { generatePrivateKey, privateKeyToAccount } from 'viem/accounts';
 import { nitroTestnodeL3 } from '../chains';
 import { arbOwnerPublicActions } from './arbOwnerPublicActions';
diff --git a/src/package.json b/src/package.json
index 3c64c48a..6a277446 100644
--- a/src/package.json
+++ b/src/package.json
@@ -51,7 +51,7 @@
     "viem": "^1.20.0"
   },
   "dependencies": {
-    "@arbitrum/sdk": "^4.0.0",
+    "@arbitrum/sdk": "^4.0.2-beta.0",
     "@arbitrum/token-bridge-contracts": "^1.2.2",
     "@offchainlabs/fund-distribution-contracts": "^1.0.1",
     "@safe-global/protocol-kit": "^4.0.2",
diff --git a/src/utils/decimals.ts b/src/utils/decimals.ts
new file mode 100644
index 00000000..3d8fc5b9
--- /dev/null
+++ b/src/utils/decimals.ts
@@ -0,0 +1,26 @@
+import { BigNumber } from 'ethers';
+import utils from '@arbitrum/sdk/dist/lib/utils/lib';
+
+export function scaleToNativeTokenDecimals({
+  amount,
+  decimals,
+}: {
+  amount: bigint;
+  decimals: number;
+}) {
+  const amountBigNumber = BigNumber.from(amount);
+  const result = utils.scaleToNativeTokenDecimals({ amount: amountBigNumber, decimals });
+  return BigInt(result.toString());
+}
+
+export function nativeTokenDecimalsTo18Decimals({
+  amount,
+  decimals,
+}: {
+  amount: bigint;
+  decimals: number;
+}) {
+  const amountBigNumber = BigNumber.from(amount);
+  const result = utils.nativeTokenDecimalsTo18Decimals({ amount: amountBigNumber, decimals });
+  return BigInt(result.toString());
+}
diff --git a/src/utils/registerNewNetwork.ts b/src/utils/registerNewNetwork.ts
index 0aaf09fd..bdd926c6 100644
--- a/src/utils/registerNewNetwork.ts
+++ b/src/utils/registerNewNetwork.ts
@@ -4,6 +4,11 @@ import {
   getArbitrumNetworkInformationFromRollup,
   registerCustomArbitrumNetwork,
 } from '@arbitrum/sdk';
+import { testnets } from '../chains';
+
+const isTestnet = (parentChainId: number) => {
+  return testnets.some((testnet) => testnet.id === parentChainId);
+};
 
 export const registerNewNetwork = async (
   parentProvider: JsonRpcProvider,
@@ -21,6 +26,7 @@ export const registerNewNetwork = async (
     confirmPeriodBlocks,
     ethBridge,
     isCustom: true,
+    isTestnet: isTestnet(parentChainId),
   };
 
   return registerCustomArbitrumNetwork(arbitrumNetwork);
diff --git a/yarn.lock b/yarn.lock
index 20c775ca..77b52ca1 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -22,10 +22,10 @@
     "@openzeppelin/contracts-upgradeable" "4.5.2"
     patch-package "^6.4.7"
 
-"@arbitrum/sdk@^4.0.0":
-  version "4.0.0"
-  resolved "https://registry.yarnpkg.com/@arbitrum/sdk/-/sdk-4.0.0.tgz#8eb2deed1a438250acb4084a4bb8fc7eae7659b6"
-  integrity sha512-wNZFRs4yYxd6Pyc6xEjksp3C59PikmmVPIw49ceMoLY5D0e6xJt2nuA7jjsemDgRe7q6EvLFvHAY2At6XUWrkg==
+"@arbitrum/sdk@^4.0.2-beta.0":
+  version "4.0.2-beta.0"
+  resolved "https://registry.yarnpkg.com/@arbitrum/sdk/-/sdk-4.0.2-beta.0.tgz#864e38797d9f25e0b0d6a5f0147d60bd5b5db3b6"
+  integrity sha512-Q22DqEYzlkspvx6h9LUgTFgpUr9PNtPiyp4hTaODOdNl+cbpVAz6G9x04iMAnNia9sP0KffhDD5WxS4CzFrFFw==
   dependencies:
     "@ethersproject/address" "^5.0.8"
     "@ethersproject/bignumber" "^5.1.1"