Not sure what power level but I fill up before I leave to go to the track and our track is an hour away. I run with 3/4's to half most of the time...if your racing in a series then I would be concerned about fuel and weight. For a weekend guy hitting the track every now and then...I would just run a good amount and not worry about it. Besides the fuel tanks in these trucks sits in a good spot just infront of the dif. If anything it'll help you hook if your on a street tire or just hook up in general.
If I don't run at least 12 gallons of fuel, My pumps see fuel wash when I launch. (stock fuel tank)
before going built I always ran at least 8 gallons.