No problem Allen. I don't know if you have read the JL .21 thread, but you can pull a shim out of the Killer 9 (JL .21 & Killer 9 share the same internals)since it is so overshimmed from the factory. It is coming shimmed at .8 -.9 with four shims, after break in you might want to pull a shim out to lower compression and make a little more power. I will be running my Killer less one shim this weekend at a well heated indoor track to see how it goes.