I was validating my compression ratio tonight & took a few screen grabs along the way for your viewing pleasure. The numbers are only meaningful to this particular design, but just demonstrating my approach. Of potential interest is the relative CR impact of either shortcut omissions or by diddling the dimensions just a bit. I was never able to do this without a Cad tool before, but now I can. FYI the target min CR is +9:1 so mission accomplished, the balance can be head shimmed. Here is the section view. The head has a boss that is slightly submerged in the liner & it has 16mm radius hemispherical combustion chamber. Valve cups are both 10mm OD & 0.25” glow plug, all at 22 deg. Piston deck clearance is 0.8mm.