I've lost a couple of small frags to mine- I panic every time he even shifts to one side thinking he may be going to move.
My RBTA just keeps getting bigger and bigger. I sometimes hope he will split (so I can get rid of half), I've stopped feeding him big pieces of food- if my Clowns didn't love him so much I would just as soon have never gotten him.
This is IMO the trouble with starting a "Mixed Reef"- you're not quite sure which way your interests will go and you end up with things you wish you hadn't purchased. I just moved a pile of softies over to a fish only tank so I'd have more room for my SPS.
Never thought I'd get on the SPS train, either. Go figure.