Tim
I've done a bunch of guns, mostly Bess's for re-enactors. I use .032" thick 1095 spring stock I pick up at Dixons. They all have worked fine.
I grind the frizzen face as smooth as I can get it. I then flux it and tin it with tin/silver plumbing solder. Next I shape and bend the sole material to fit while in the annealed state. I usually shape it with a long "handle" extending off from where the top of the frizzen would be and file a little notch just at the top of the frizzen. I heat the sole up to red-orange color in a MAPP gas torch and quench in diesel fuel. This makes it brittle hard. Sand the convex side of the sole nice a bright clean with emery paper. Apply flux and clamp it to the frizzen where you want it. Heat the frizzen, not the sole, until the solder melts, no more. Once cool break off the handle and grind the spot where it was smooth. Half hour job!
Best Regards,
JMC
John Cholin