The hot glue didn't mess up my cube, you can peel it off. It's just really stringy, and it gets everywhere, so it's difficult to apply, but perhaps that's because I have a dollar-store hot glue gun. Even so, I think it would be difficult to apply to just the spots that require it. Because the caps cover the entire top of the cubie, rather than just being an insert, the place that requires the glue is all around the edge of the cubie, so the glue squeezes out when you place the cap on. It is difficult to peel off just the little amount that squeezes out, and it's difficult to apply a constant amount of glue around the entire cap. I think the design just doesn't make sense -- it should be an insert, like the original store bought cubes.
I'll have to try the paper or clear cling wrap, as you've mentioned. Thanks for the tips.
I'll have to check out Dan Knights' webpage. I can't see that super glue / crazy glue is good... after all, what if you want to adjust the tension? But, thanks for the link, anyway.