Thanks for the input guys. Again however I want to emphasize I am not interested in cutting the rails off. The Drip rail stays in place is filled & molded into the roof line with a nice flowing radius. I have done test spots & get seperation @ the roof line & drip rail both. It may have to do with the extreme heat as I live in Las Vegas & it's hard to tell how hot a black trucks surface gets with that desert sun beating down on it, but the expansion of the metal over time causes seperation of the materials.
I am seeking other ways to fill it that will stand the stress & expansion csused by the extreme heat here.
Bondo failed, fiberglass resin failed the test. other options?
1 old fashioned lead ?
2 metal to metal aluminized bondo ?