I bought these for my spouse who is short, athletic-build, with large quads and butt. I bought a small, and while it was long in the legs on him, it fit everywhere else. I must however dock a star because of the odd pattern around the butt. Instead of the seam running along the crack, it has two seams on the cheeks. This undefines his butt which is a big miss, in my opinion and his. I think if woolx altered where the seams were on the back, the resulting legging will make everyone happy.
As for performance, it worked perfectly.