Seaball,
I don't, and won't unless I get decent data use 16 awg wire in my sedan. I think the current draw is too high and the ampacity of the 16 awg could be an issue. I do use 16 gauge wire in my 12th. It's a very light car, has way less amp draw under acceleration and if you run mod then you try to manage your throttle through the race anyway.
Do you really think you would be able to tell the difference in acceleration between 4.18v to the motor and 4.144v at the motor? this being a 0.9% difference. I've been racing for 12 years I'm not sure I could tell. Also considering the wieght and handling tradeoff's. In 12th class there may as well not be a wieght limit for the car it's so light.
Over the weekend if I have time I'll measure the volt drop on some wires for a given length at 30A and see what it tells me. I'll post the results when I have them. I can't promise to have the time as I'll be racing on Sunday.