If you choose to mig weld it. Here are my thoughts:
1. Scuff the area of the tear with a angle air tool and 36 grit wheel.
2. Hammer and dolly the fender back into place.
3. Clamp the tear so that you have a perfect butt joint. Remember, your butt joint ends should NOT touch. You should have about a 1/16th inch gap (about the same thickness of a cut-off wheel) which is filled with weld. A butt joint that is touching and welded WILL crack later.
4. Tack the tear as in the picture, about every inch.
5. Then go back and start to fill in the welds. All your welds should be spot welds but you can use a 1/4 inch or so of a bead weld. DO NOT be tempted to bead weld over a 1/2 inch at a time. That WILL cause the metal to warp. Put a couple in each gap (between the 1 inch gaps) and then immediately put a cold damp rag on the weld to cool it. Continue until the tear is completely welded.
6. When done, metal finish as usual. If you're on your mark, there should be no filling required.
[img]
http://www.redskyguideservice.com/MigWeld.jpg[/img]
