Been away from the Spyder for a couple weeks: trips to see the eclipse and then the inlaws. Today I bought a couple sheets of 22 or 24-gauge aluminum sheet to do the inner clam panel with, when final. I've bent some scrap this thick and also some flashing, which is about half as thick (and wrinkles quite a bit), working out the shapes and planning. Here's the center section from that first try with the thin metal.
I think the thicker metal will look better and also be a lot stiffer. I also think I'll be able to braze it together rather than relying on rivets and body filler.