Hi Chris
I believe the competitive guys at Coastal & STCC are running the Corally/Graupner (I think thats what it is) 21.5t motor.
Its significantly quicker than the others but not BRCA legal (but this doesn't matter at Coastal/STCC) due to the way its constructed.
Might be worth investigating before you (potentially) waste any money
I don't think even a guy of your talent would be competitive at the STCC without one...