don't do it if you want the patches to hang on more than a couple years - there is a special fiberglas resin intended for bonding to metal, but even that doesn't hold long with the difference in temperature response between metal and fiberglas
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics