[suicideneil]

Not too low, maybe a little high infact. The 8xl will run a little hotter than the 9xl, so gearing down a touch is advisable- aim for more like 40mph; going faster than that will be hard to control. Easy way to know if you are over/under geared:

Hot motor + cool esc/batteries = under geared. (not enough load on motor, so it over revs)
Cool motor + hot esc/batteries = over geared. (too much load on esc to supply amps, causes it to heat up & thermal/fail)

Generally speaking anyway. You will want a fan on the MM and run a ubec to power the tx & servos (disable built in bec via programming or remove red wire from rx lead to esc).