Since you're already familiar with compression tights, you should have an idea of how they fit - very snug if they're going to serve their purpose. I'm shaped differently from you, but I find that CW-X tights run large - I'm a solid Medium in most running shorts/tights, but on the small end of Small in CW-X. I'm almost tempted to try on an XS next time I'm in a store, but I expect those will be too small for me.