shotbirdsc said:Both pulleys give you the same result if you change their size as the jackshaft drives the SC pulley.
SC pulley is small and if you make it smaller you have a chance of slipping and then loosing the boost and tearing up belts. If you were only going 5% I wouldn't worry about it though.
Jackshaft pulley is a lot larger pulley so taking 5 or 10% off of it won't make a difference in terms of surface area and slipping. Costs more but easier to install.