I'm glad I did a search before I posted this exact problem. I just installed a UN-55 with aluminum cup and it's loose too. I didn't notice when I installed it, but a few days later I started getting an annoying clicking noise from the frame with every hard pedal stroke. It was easy to reproduce by squeezing a crank arm against the seat tube. First I tightened things up and the noise went away for an hour or so. Then I took apart the BB and found the loose cup. I shimmed it with high temp metal chimney tape until snug (two wraps), reinstalled it, and it works just fine now. I didn't measure (I'm not that OCD) but ten mils sounds about right. It looks like a defect to me and I was just going to check here before contacting the vendor. Since I bought it online, it's not easy to return, so I might just leave it as is.