9.5 is best for ur combo, that’s what I have. Tighten’ing what u have will work, & help manage ur 60 on the bottle, u will lose a little 60 on the motor.
If u go to a brake, u might need a set of adjustable rear shocks. I had to change my setting for the t-brake, b/c now the car acts like a stick car & shocks the tires instead of the chassis being preloaded when foot-braked.