When I restored my 71 Bee about 10 years ago I used plumbers mastic or whatever it was called.... It seemed about the same color and texture as what I scraped off. It can rolled and shaped as necessary. And for the plastic I used vapor barrier from any local building supply store. I didn't really know how the plumbers mastic was going to work out, but I had the panels off recently and I was pleased it held up nicely, I could peel the plastic off and reapply.