Why not mount mirrors on each panel of the door. You could probably find some inexpensive, frameless mirrors at the home center or cut to size at the local glass shop. While the resulting reflection probably won't be as "perfect" as continuously mirrored surface, it should be "good enough" for most purposes.

I think this might work, though we worry about mounting them to the vinyl garage door. I will call the local glass company tomorrow and see what they think.

Curious — looking to do that same. How did it work out for you?

I ended up just buying a 4x8 sheet of mirrored plexiglass, gluing it to a piece of plywood, and leaning it up against the garage door. It works alright except that I did not buy thick enough plywood, so the mirror has a bit of a bend in it. It serves the purpose of allowing my dancer to see foot placement, turn-out, etc... but it isn't what I'd envisioned. I hope that helps you!

It does! Thank you!