(Decking) Whats the limit

Wouldn't the 745's put me at 9.6:1? The rhs heads are 67-68cc. Either way, I've decided to go with hypers. After talking with KB this morning, they turned me on to the kb416's that are a 25cc dish that should put me at 9.3:1(perfect) and require less milling. He said being that I live in ND and plan to drive it in the winter, that forges requiring twice the cylinder wall clearance do to expansion and can actually shrink in the cold resulting in rocking and hitting the head with tight quench. He said hes even seen forges in really extreme cold conditions shrink so much they gall the rist pin. He said hes seen hypers live up to 600hp on a healthy tune and good tolerances. Not to mention there $100 cheaper and use 5/64th's rings. Seems like a good piston for a 475-500hp street motor that will never see laughing gas or boost or 6500 rpm. You just need to fallow directions with ring gap. since the sylicon transfers the heat to the rings more than a std cast or forge piston. This is getting off topic though, I just wanted to know how far a guy can mill the heads or block b4 you have to stat shaving the intake. Idk if there a general guide line.

Thanks moper