Back in the dark ages, (1960's) I can remember mail order places like J.C. Whitney and Warshawsky (same company) selling "high compression" head gaskets- - - -.030" thick solid copper gaskets that were supposed to give all sorts of performance gains over the thicker composite gaskets that were in common use by rebuilders. Of course, they offered no advantage at all over the .023" thick embossed steel shim head gaskets that most manufacturers used as original equipment.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!