I don't have mimics but I do have a Lt. Tang in my 210 and he is getting big. Bought him a tick over a month ago from Live Aquaria which they listed has medium small. About 3 1/2". Anyway in a little over a month it grew a lot and is now pushing 5" if not a tick more. Fast swimmer, friendly to other tank mates, and eats everything to include two sheets of nori a day if I feed it. Both green and purple nori. Anyway your tank is wider but figured I'd toss out the movement and personality if it helps on the Lt. Tang. Beautiful fish but getting large fast which I wasn't considering.
Only reason why I also posted is because I was considering also adding a mimic for a 2nd tang option. It was either than or a kole tang since the Lt. isn't has active with regards to scraping rocks.