I don't like a whole lot of splash most of the time so I don't worry about cupping the face. I have something made out of sheet foam that makes more noise than any cupped popper if that's what they want.
I also don't like using super glue on the bodies. Yeah for putting it on the shank it works great but not over the whole body. It does seal it up good for sure but it also sands like a rock too. And I want/need them really smooth before I paint. The best thing I have found so far is DAP Patching Plaster. It sands really easy and leaves everything smooth. Then a coat or two of primer, sand again, and then paint. It's all overkill though. I should just take some sharpies to some bare balsa and the fish wouldn't care but it's so much fun to tinker.
I install the hook/shank after I have the body formed. Super glue it in and then fill the gap with elmers glue mixed with the balsa sanding dust. I like the idea of having that hook or shank to hold onto while using the belt sander but I would either nick the hook point or bury it in my hand.
Tails? Silicone is good, Marabou is good, Hackle is good. It's a popper, you can't go wrong.
Your flies look great Billet.