Recommended Fuel Tank Size

[ADiCarlo]

So I'm contemplating putting a fuel cell in my car. The ultimate goal is to have a turbo LQ9. Reading up online I see mixed reviews in terms of fuel mileage, my goal is to have a car that can carry enough gas for 300 miles.

Would a 15 gallon fuel cell work? From what I've read people get around 20 mpg but I know for a fact that I'm heavy footed and don't want to be stopping for gas every hundred miles.

Any input would be great. The car will see track use - what's the average consumption during track days in regards to road courses outside of the parking lot auto x.