Auto body repair & detailing: Repairing over stretched metal, striking area, mike lisa

Question
 Hello to Mike & Lisa,     My queston is: My son stretched the roof of his 1971 Beetle, by using the wrong hammer while knocking out a dent. Befor he looked to see it was already stretched.When I was in high school I worked for a body shop. That was too many years ago. I know there was a method to tighten up the damage a 21/2" diam. I believe it is with in the repair limits. All I can remember is I believe they heated the area outside this 2 1/2 area and using a torch,then using a dolly and a hammer beating around the outside the area it pulled the metal enough to strengthing the inside of the hole. I need help folks. it is now 50 some years later and my memory is fading. Would realy appreciate your answers. Jack

Answer
Hello Jack,
   First, try using a shrinking hammer.  This hammer has high points on the striking area instead of being smooth.
If this doesn't work well enough, the proper way to shrink a metal panel is;
  Heat the high spots directly with a fine tip on the oxy/cet torch.  Heat the highest spots first the
 size of a dime until red hot not white hot, tap it gently with a regular hammer and cool it immediatly with a wet rag.  Repeat as necessary.
The cool water is bascially what will make the shrinking process quick and obvious so you can move on to the next area.  An ice pick comes in handy for any pesky spots on  cold spots, a little trick of the trade.
Thank you,
Mike and Lisa