Just to be clear..... the .039 compressed Felpro is the Felpro 1008. The .050" compressed Felpro is the 8553PT. 2 different gasket PN's; the 8553PT is the standard kit PN.
If you go from the .050" to .028" think head gasket, that is about 0.35 points in compression so is not negligible. You will indeed feel it on the butt-dyno. How much trouble anyone would have on their particular engine with the Mr Gaskets, IDK. But I'd take the precaution to at least have the heads skimmed.
I used very similar composition gaskets to the Mr Gasket for thousands of race miles on my turbo Mitsu rally engine running 14-15 psi boost. Blew a grand total of 1 when the engine got hot and the head warped a bit. Otherwise, A-OK. So it seems to be a mixed story.
