I'd like to see all the short spark timing advocates list the CID, cam duration, compression ratio, and peak rpm of their combos. Get enough cross section of data and you will realize what impacts what. Over and under square motors are not exactly the same from a spark timing standpoint. And its not just chamber design.. but induction speeds are quite relevant here as well. General rules of thumb recommendations will give you general rules of thumb performance. Read the plugs and use the clock to tell you what the motor wants.. not what people think it wants based on entirely different combos.
