unfortunately the damage on that side is done. Take it from him immediately and give it to someone who knows what they are doing. Lots of guys wont weld that entire section as warping is almost inevitable. they put a recessed edge on a replacement panel and then glue and spot weld in place. I had a panel beater of 25 years fill in two of the whirly bird (ex -copper) roof holes in a WB. one came out perfect the other warped to the shit and took a large amount of bog to rectify!!! He charged me a $100 so i didnt have a leg to stand on