I did it 20 years ago to a bike, put a 10sp wheel/cassette in, and used it with friction shifters without problem. It actually shifts much better than the old 6 or7sp it replaced, and is quiet. The ramps on the HG cassette make the shifts really quick with only a slight shift of the downtube lever, and it always lands in gear because there is so little room between them. There is none of the clanging sound. I will be riding that bike next week when I'm in Seattle with my son. He took it with him so I'd have a bike to ride when I'm there, where I originally had it built back in 1981.

Also, 11sp wheels are actually 131 spaced, at least Shimano wheels are. They stole that extra mm to give it more room. An 11sp freehub is 1.8mm wider, so it uses that 1mm and gets a little more from shaving something down a bit. It fits fine in any 130mm frame, but that's just a little more stretch for a 126 frame.