from my testing you need to go up a pinion from what you would usually run on a stock motor,they have the torque to push a bigger pinion as you have found out
more fets do let more current through,which in turn helps this motor open up,my 3x2 f1 flies with the pn motor and around the equivalent of a 9t pinion and 32t spur(belt drive)
once a bigger pinion was installed on both my hfay awd and mr02 i could keep up with nobby and his s5 motor car easily(as well as making them more drivable)