Believe midrange allows up to 8 hp, so a hf212 fits the category as long as it follows a strict list of mods keeping it class spec. Pretty sure It will allow a billet conrod and flywheel to keep the "boys" safe. Will limit springs to 16 lbs probably to limit rpm. Won't allow a stroker crank, don't think shaved heads are allowed. Doubt crazy cams will be allowed. Don't think it will be allowed to go over 5k rpm, as hp=torque*rpm/5252.