Re Shimming

the 101 is a guide so you can make informed experimentation with your go engine. The only way to see what works for your set up is to experiment with different plugs and head shimming. Remember what may work for one person may not nessesarily work for your particular set up.
And the good advise is to contact your engine modifier for particular advise on that engine. They are the best person to help you with this.

MM