hmm.. I race mine.. even against xray touring cars onroad.. I have yet to be beaten.. and it's a stock chassis.. I don't think it's that big of deal..
as for the bevel gears.. you have to shim them with an 8mm shim.. look on towerhobbies for a shim..
BTW.. why are you using reverse if you're racing?? If you're competitive with fast racers you shouldn't have to worry about reverse... I am doing it for fun.. not for a real challenge.. but to each his own