if your going too stick with 20% after a gallon you can take out the thinner of the 2, that will put the squish at the lowest you want to be at, but after you get quite a few gallons on the engine just check once in a while to be sure the head button and piston aren't pitting, if you see some signs odf this place the shim back in, the motor is set out of the box to run 30%, but just keep and eye on it, i would probably just leave it in unless the timming was modded, otherwise if you like the way it feels just enjoy it, if you have one try using an 086 pipe on that engine it's real nice
