I fixed some of the low spots with Bondo and spot putty and sanded and scraped it a lot, eliminating all the finger marks reproduced from the clay.
I also corrected the off-center back end. Notice the black line (the true centerline) and the filled-in red groove (the erroneous centerline). I couldn't believe I'd gotten it that far out of whack. It's not perfect, but I don't think anyone would notice unless it was pointed out to them, that anything had been wrong. I won't know for sure until I put a coat of primer on the darn thing. The multicolor look kind of camouflages it, makes it hard to see what the surface truly looks like.
I set some furniture nails in around the eyes to act as the "rivets", and set the thing up to be painted.
After a good coat of primer, it looks pretty good! There's a few rough spots and pinholes to be filled, but not bad.
Now it's time to make the fin. I started off by cutting the rough shape out of 1/4" birch plywood.
Then, to make sure the bottom edge fit the helmet exactly, I put some wax paer on the helmet, coated the bottom of the fin with Bondo, and pressed the two together.
After sanding off the excess, the fit was very close.
Then I shaped the front to the proper "knife edge" and mounted the fin on the helmet temporarily with three screws.
Next up: a coat of primer on the fin, sanding and filling any surface defects on the fin and helmet, and applying the fake welds. I should start on that tomorrow...