So we can see here that it doesn't look like I can shave enough off:

I went to Hobby Lobby over lunch and it looks like I going to need to make a mold and tap out some holes. I saw some Alumilite products that look like they would be durable plastic.

The plan would be to cover the screw holes and take a mold. Hmm, I might also look to add a bit of width on the hole bases. I.e., I probably need another millimeter or two of wiggle room. 1 for the hole and 1 for the rim.

But once I have a mold in place, I will also be able to make my own spares and not be so cautious with what I have. :->