I would use araldite rapid as it does not set quite so hard as the normal type so is not quite so burdensome if you want to fill a dent. i.e a little at a time and then sand back to a flat surface. The isopon stuff is quite brittle and needs a good "key", something like araldite needs rather less.
I think soft solder is unlikely to stick to the frame, some type of two part epoxy applied in small quantities may be a better solution.