Good thought on the elastic. I plan on wrapping it under the instep of the shoe, the part in the middle that's raised and doesnt really touch the ground. But if i decide to take it to a Con and will be on my feet all day, i'll definitely do something inside the shoe.
I'm happy with how they came out, they're not perfectly accurate, but i think they work, and they don't interfere with my walking. I'm building the ankle pieces right now, the piece that goes between the calf and the top of the shoe.
Miso,
These are $20 shoes from Academy. and they actually don't move around inside at all. the foam is rigid enough to stay in place. I started with the bottom of the boot. i built it really close to the size of the shoe, then built upwards from there, till the pieces met at the mouth of the shoe. I just slide it onto the shoe and it stays in place, the elastic will just make sure it doesnt ever flop around if my feet get moving fast, like going up stairs.
Gotta make sure you use small shoes on your feet. I thought about buying some CROCS and attaching it directly to the shoes. But CROC sandals are so wide, foam on top would have made my feet really wide looking. I would have looked like an Iron Duck.