Remember that detonation can create enormous cyl pressure.
Maybe it's not the gskts or o-rings.
Just curious if that plug was damaged by mishandling, or other .
Good luck .
None of the plugs were damaged. One was fouled a little. I run my fuel mixture a little on the rich side to start with and that is what 7 of the plugs showed. It was just #6 that was fouled and that was the one that the gasket showed as the worst.