Ha ha,.. I was wondering who bought the rest of those things! I got 20 and to be honest, they were so cheap that I can see how you thought you were buying singles. They ain't perfect but they seem to be just fine to replace bad reels.
Ben. One thing you might try to keep your 7" reels from scraping (flanging),.. if it's always on the outer part of the reel, you might adjust it the take up side a little farther out (is it shims/spacers on the Otari?). I have that problem with my Technics if I adjust the take up side dead center. I think that some reels are just made a little thinner so the outside flange rubs. If you have any of those awful gray reels that Columbia tapes are often on, I'd replace those just because they're a pain to thread and those reels are very prone to warping. I don't like the fact that you can't see the tape wraps/condition either.