I get your point there but I sure might investigate this as an option for a few spots I have that really aren't even generally speaking visible....only visible when taking pieces of the car out of the way, etc.

 

You could always use a spot welder also and put in small patches. That's how I fixed some of my smaller holes. After that I took a grinder and just ground down the edges around it and then fiberglassed the seam and over that applied body filler. With the heat being applied it kind of sinks the seam - you'll need to weld the whole way around. Then with the fiberglass and filler you can't even notice it.