Well, FD, you've hit the limit on those motors. It's not a question of how much copper you can get in the slots. The problem is the clearance from stator to can. And just to drive you nuts, they're all a little different. Some can tolerate 3 layers, some can't. And of course it's even trickier when you're building a pusher.
I had an ABC that was tight front-to-back and wanted to do something interesting, so I made a 6T 22awg. It was a fine motor, but I really liked the way it looked: