In reply to top cat:
I wear a size 41 Scarpa Rebel Ultra which has a very narrow heel. The Petzl Lynx fit perfectly and I wouldn't be surprised if the heel section is the same on their other crampons. You just have to adjust the fit so that the parts that contact the side of the heel sit slightly further forward. You just have to tinker with the heel locker and the front section to get a good fit.