So I am not a professional and I have not seen 'all the short cuts' but I have seen a few rockers filled with spray foam or heard of chicken wire used to hold filler......I am sure the pros here have seen much more, but check this out....

I am sanding the lower portion of the corner behind the wheel well down to the metal. There are these mini-spots all over maybe a 3 inch by 3 inch square. I could feel them by hand but could not really sand nor grind them away.

Checking the back side of the panel I found the source. The guy that painted this truck in 1994 used something like JB Weld or one of its equivalents to back fill pin hole rust. The back of the panel is lined with the epoxy type material. I guess as the excess pushed thru the holes it was sanded down, skim coated and til now know one ever knew the difference.

Not being a body guy I would think that would have rusted more, and bubbled the paint after 25+ years but I guess it held up over the years.

I felt sort of bad cutting it out and replacing the section.

Just a funny to start the week.