I have some really bad rear quarter fender rot, it must measure atleast 6 to 8 inches up from the inside corner of the wheel well. I don't think I can cut and fold them, is there a way to cut them and then weld in a "cap" of sorts to cover the hole? Or can I just fiberglass the hole?

 

Rustys Off Road has some really cool aftermarket fenders front and rear, not cheap but really cool.

 

You should weld in New metal. Fiberglass won't work there except for patching real small holes.

 

How about "cut and fold" what you can. Pop rivet some sheet metal over spots. Fill with expanding foam, trim excess foam and paint with spray on bed liner. It will look great, especially after it's coated with mud.

 

I have it really bad there. So while I'm replacing rockers were gonna cut it up to the line above where most cut and fold it to. Then just going to weld in new metal, por 15 it, then bed liner