Oh for sure, that's why I am using 10awg wire now, for two reasons:
-Resistance of course to match the connectors...
-but it sucks heat away more heat from components, motor, esc (especially on a Quark)
I wouldn't have gone with 6.5mm plugs if I didn't switch to 10awg, and it does make a difference in temps, they are noticeably cooler than 12... as well, when you are WOT, there are large currents like you said, and 10 will feed the system that much more voltage.
My next upgrade would have to be a larger motor of course, as a 1512 would obviously have higher resistance than a larger unit such as a 1515, or a T8 truggy motor.
Whatever you can do to make a more reliable high powered setup, I'm all for it.
