Red high temp RTV.
I bought a 2' x 2' sheet of .002" laminated aluminum .048" thick for $50 from McMaster-Carr. I made two gaskets and installed them using the red RTV. I'll let you know in a couple of weeks if it's better than just RTV. I've tried 2 or 3 gaskets over the years but the red RTV worked the best. I think the soft laminated aluminum will work.
See ya'll in Ohio in June!
Dwight