combustion chamber question

Personally, no tighter than .040" on the squish distance for a street engine that You want to build "one more time". Carbon build-up and overheating for any reason & that
gap will close up fast. I could list all of the things that can happen when the edge of the piston starts clipping the head, but none of them are increased power, decreased
maintenance, or a longer engine life. Same for compression, carbon does two evils, raises the compression & increases the chance of detonation by it's very presence.
Put Me down for no more than 10.5:1.....as long as You have the fast-burn from your .040" gap working for You.