5.9, max safe compression?

BTW, running your original numbers (.050" in the hole) and 62 cc chambers, I get 9.35/7.5 SCR/DCR at 0 ft elevation. Decking down another .028" for .050" piston to head clearance, I get 9.9/7.9 SCR/DCR at 0 ft elevation.

Since my SCR numbers are different, that is why I asked about the piston models. Have you cc'd the dish in the pistons? I would not expect quite as much dish volume at the 11 cc's you list for 405P's. I also don't get .050" deck clearance with a stock deck and those pistons.... so things are not quite adding up yet.

Edit to add: So are these H655CP's? The 11 cc dish makes sense now. The .050" stock deck may be a bit off but is close....