Originally Posted by DanielC
If you can, back up the area welded with a piece of copper.
Even a piece of copper pipe flattened will be a huge help.
Yep, I do the same thing
You can just go over the spots with the welder backed with the copper piece.
Or you can just fill the pin holes with fiberglass. I did that with my old car back in vocational class when I had the same issue as you and it came out fine.