i am running a 4300 in my 1/12 scale in the 19 turn class. yes there is more weight, but it really did not change things much.... i think the motor is like 30grams more ?? (sorry it is in the car so i cant tell you for sure).. at our next big race i think i am going to get a 13.5 and run in stock also. the best thing with the brushless.... you have more time to make changes to your car. and with 1/12 scale sometimes that is a good thing...