But it would be better under scrutineering to have a slightly undersized tank, instead of being oversized? Otherwise, an example would be in a power limited race (full scale): The limit is 500 HP. Some just have it set to run at 495 to account for variations that would alter there power (air temp/density) but there is 1 guy tuned at 499 on a hot day. Today, it is cooler and he is actually running 503 HP, so that makes him over the limit, just like having that extra bit of fuel in the tank to extend runtime.