I have known some good welders, but I think that would be pretty hard to do without heating a larger area of the cylinder and destroying any heat treatment the cylinder has. Also, remember that the stop notches are the thinnest part of the cylinder wall, no place to go heating things up.
So, no, I don't know anyone who has tried that technique. But very often the steel from the notch is simply driven to the edge of the notch, leaving a sort of a turned up "lump" on the edge. In that case, what works, with care, is to lay a flat piece of steel on the cylinder, contacting that turned up edge, then tap it with a light hammer. That forces the turned up metal back into the notch and tightens it up some. (You can tap directly with the hammer, but using the steel keeps from having multiple dents from the hammer blows.) Of course, this is not a permanent fix, but it can help get a bit more life out of an old gun.
Jim