OK.. I'm reading this thread and you folks are getting me worried...
I applied fiberglass to the roof of my truck. I was told it was fine..
SO let me detail what I did and give me your thoughts.
I stretched the cab of the truck and it wasn't quite level,.. so we added fiberglass to fill the low spot. We did this:
Sanded the metal with 40 grit paper.
Put on epoxy primer.. sanded again with 80 grit.
Then we put on a layer of resin, a layer of fiberglass mat, resin, mat and then resin (all at once). Stuff is hard as a rock.
Then we put fiberglass out of a can on top of that to help with the small low spots (some on top of the fiberglass/resin mix, and some on bare metal), and finally bondo to make final adjustment to make it perfectly smooth.
We sanded with 40 grit between each application.
SO please tell me I'm not going to have any problems...