3 diff balls.......wow thats a first. I think there is other ways to save weight in the drive train, but if it works for you run it. Im running Plaid fronts and Purple rears. Are you runing 64 pitch on you car??? If so you might want to run the Stock spur that would probably save you as much weight as you taking the diff balls out. I have noticed that the diffs on foam tires are very critical and you would want them to perfom to the best of their ability.