Addressing only the fuel volume problem:
Check out the "burrito tube" mod that people do to their hawks here, supposedly you can fit it onto your front forks with "quick fist" clamps and then put a MSR 30oz fuel canister in one. You could do both sides and have about 1/2 gallon more
- Burrito tube
- Quick fist clamp
- MSR 30oz
Personally I'm a fan of Rotopax for fuel transportation, the offer a wide variety of fuel canisters and mounts.