[suicideneil]

Old rule of thumb:

hot motor + cool esc & batt = undergeared
cool motor + hot esc & batt = overgeared
hot everything = way overgeared
cool everything = just right

I think you should maybe try gearing up a little with 5s first before going to 6s- the truck may not be a lead-sled but the MMPro is generally best pegged at 4s lipo when used in an MT ( though with a ~2000kv motor too ). See how the temps react and take it from there..