Bondo, or body-filler, comes in a lightweight version these days. It is filled with glass spheres that are themselves filled with trapped air. This bucket is 3 liters (0.8 U.S. gallons) and the shipping weight is 8 pounds. My estimate is that I might fill all of my existing dents on both roof halves with 3 liters.
The question becomes: does an additional 8 pounds, plus the weight of paint, on a Trailmanor roof section add so much weight that it’s not going to lift well, even with adjustment of the torsion bars? At least one of my roof halves has lots of range in the torsion bars, we’ll see what I can persuade the other to do.