Hmm.... where to start.... The counter balances on the control surfaces are a good start, also possilbly incerasing the aileron area as well. I have a tower "extra Special" profile kit at home. If the P-51 is anything like that kit, it will be heavy. Reduce the lite ply in the kit as much as possible, use the lightest components possible and the aircraft may have a fighting chance. I am not really qualified to say if the servos should go in the tail or not, but my guess would be to leave them where they are, remember a little weight change in the tail leads to a big weight change up front to compensate