I know it seems like a good idea, but it doesn't work very well. It will crack at the hem flange.
I understand and agree with you.
What if on the 3 sides I bend the hem up 90 degrees, and along the back lip I grind the edge away? (until I break through the hem)
Then I separate the inner and outer skins, and make my repairs.
Then to put it back together, I hammer dolly and fold the hem back down on the 3 sides. Then I would weld the lip area, at the edge that I ground through?
Do you think I would get warping?
Any suggestions?