At the club where i race they have a mini indoor competition. the rules are basically stock mini of swift, no hop ups but the electrics dont have to be original. We usually use Tamiya M grips on the front and the stock tamiya tires that come with the kit on the rear. The only mod that almost everyone has done is lowering the mini so that the arm are level. The last races most drivers switched to M grips front and rear which was faster but the car would traction roll in the corners. This track is very small and we aren't allowed to use any traction compound. Even for cleaning the tires only water is allowed.