Well not that I don't believe Kal(eb), I do totally believe him.
However, my experience with Underworks is the opposite.
I got the 997, so maybe that changes things. but according to their sizes, I should be a large. I got a small, and it works well on me. actually it's starting to stretch out now and not bind as well. but if I had gotten a large, for sure I would have had to exchange it. which is just a hassle.
If I were you, I would get a small or extra-small.