It also depends where you want your power at I chose to go with Hotcam stage 1 because of the mid range. I built my bike for hill shooting and wanted to be in the mid all the time. If you sand drag or dune alot you might be better off with the stage 2 for more top end. As far as 100mm,102mm it all depends if you want to bore your jug or just deglaze it. With all this being said the meat of your power is the porting!