Got the inner sleeve off by chiseling several grooves in it. Worked great!
Tried welding a washer to the outer sleeve, and then pushing on the washer without success. Each time it just pulled away from the sleeve leaving a void in the sleeve where the weld was.
Tried chiselling the lip down and then pushing on the folded metal, but the metal just folds back again and breaks off. There isn't much of a rim on it anymore, so my next step will be to chisel all the way down the side, and fold it in on itself.
I just hope I don't do too much damage in the process. It's starting to look like a caveman has been working on this. Will get back on it either tomorrow after work, or on Saturday. I'll let you know how it goes.