installing the max .21 in my gt2 keeps the factory weight balance as well with the factory mount (you need to use the tmaxx 19-24t clutch bell and flywheel) and the motor is pretty kick ***, i have a vantage carbon fiber pipe, 24t clutch bell and a 54t spur, it stands on the wheelie bar to and over 60 mph, whomps on all my friends highly modified 3.3 and .21 jatos.