Cabin side insulation is intact on firewall and bulkhead cover so we're going to leave those surfaces alone. For now it's engine side only.
The project bulkhead cover has two metal fingers projecting from the bottom that engage two slots in the bulkhead framing. I don't see them in the photos above?
Seems like you ultimately piled on a few layers there. Original stuff, added insulation layer, metal panel. Did it cause you any pain later putting the gas tank back in? Any undesirable contact between tank and metal panel?
I'm thinking maybe just the DEI product. At the moment the intention is to get to know and enjoy this car for a year or two before she comes apart again for the full monty.
The DEI stuff seems to run about $10/s.f. Speedway motors has best price I could find.