Ok, I have a quick question for ya.

I used to re-use electrical cabinets, and one issue to contend with was welding in plugs where switches used to be. It often warped the door. At the time, I didn't know how to deal with it. I'm thinking a couple taps with your cup dolly would have squared it away.

One thing I did try ( with mixed results ) was to dent in the plug before I welded it in place. Then I would flatten it and that would 'push out' the shrink.