Balsarite
I have used it for years on both film and cloth. Works Great. I agree with earlier posts however,,,do not used it over large areas, just in the trouble spots. I use Ultracote almost exclusively now and still use Balsarite around firewalls and edges and around the openings, (servo openings, etc.), No ill effects with UltraCote/Oracover).
Steve
Puckett Model Aviation