I cut up my fender vents to use as trim rings with my newly welded sheet metal vents. What can I use as a filler on the back side of the pot metal? I'm worried about adhesion. I'm thinking along the lines of "Lab-Metal" or another metal reinforced filler.
I know it sounds redneck, but you might want to consider JB Weld. It seems to give good adhesion, and you should be able to file it into shape after it sets up.
What 3SLO5 said. 3M 08115 That's what I used to bond my vents to my fenders. Holds great and you can file and sand it after it hardens.
I've never liked JB Weld...it always shrinks on me. Panel bond sounds like a good idea, I've already got the gun for it.