I wear XL shorts as well. I wear Specialized knee warmers size Large. They do tend to wander down a bit on my leg, but usually stay under my shorts unless I am sloppy with "installation". I have virtually no calf muscles so its quite loose around my calves, but this is going to be a problem no matter what brand or size I get unless I have some custom made for me. I am not sure what my thigh circumference is, though. I guestimated and I am between 62-63cm, which is just a bit bigger/more muscular (entirely likely its just extra fat on me ) than your thighs. My biceps are 12" which is 30cm, I am pretty muscular in my upper body. What kind of Ethiopian runners are they using to define sizing?? Or are you looking at men's arm warmers by mistake?

I have given up on leg warmers. I am 5'8" with my pants inseam of 32" (which means my cycling inseam is even greater), and without fail, every leg warmer and cycling tight has been several (and i mean several) inches too long. I am not petite, but legwarmers and cycling tights sizing would have me practically a midget with thunderous thighs.