I charge my cells @ 5 amps when I race spec class. That way, the cells will get used to the demands of a hotter motor. But 2-4 amps will do you just fine.

I find that punch is somewhat important when wanting to use the throttle to change angle and attitude mid-drift. Sure, if you're full throttle most of the time, it won't really matter, but I'm just picky like that.