Ok, my inner hinge and clasp works! You need to leave at small space on the hinge side so it can open a decent amount. JUst a few inches open allows me to put my wrist in it easily with a foam wrist cuff on so it will fit firmly on my wrist.
The clasp side is pretty simple. I just used a flat headed screw for the peg, so it'll sit firmly, and won't come out. (I used superglue gel on it as well for additional strength.)
I just squeeze the bottom together slightly to release that catch, and open it up for quick removal. I used my dremel sander on the edges and outer surfaces of the cut of plexiglass to hopefully match the surface of the gauntlet better.
I shaped that cut using a heat gun, and once softened, with my work gloves on pressed it into the curved shape of the space where it was then gel glued to the cup.
These are the led flasher necklaces I'll be using to add more lights.
These are the hinges from Lowes (You could repurpose the screws for the clasp on the opposite side, but like the hinge screws, you'll need to clip them shorter, and probably want to grind the sharp tips of them down a little.)
Here it the hinge attached inside the cup. I superglued it to one side to get it to stay where I wanted it, and then driled the holes and added the screws. The screws were clipped down to slightly more than 1/8 inch so they wouldn't stick out too much, snag anything, or cut people with sharp tips sticking out.
Here it the clasp attached open,
And here is what it looks like closed.