I have had some experience with caps (mounted across the batt)
I tried small values and large (3x8800 high rate discharge caps) and noticed no real difference in punch or run time. The thing I did notice was that there was a small difference in the spooling speed of the motor. with large caps I was not able to "gear up" the motor as far because it would take to long to wind out....
Anyway I only run stock anyway so I don't know much about the effect on mods.
I am curious as to how much cooler a motor is supposed to run using caps? Does anyone have any exp with this?