[PaulatFast]

I've never had an issue with regular filler that I know of. But we don't spread it very thick, rarely over an 1/8" thick. We always fully weld our patches. We always fully weld the factory seams, grind the welds and fit/weld a patch over them. So I'm not seeing any benefit we'd gain from using it. So for something like filling a factory lapped seam, if not welded and plated, the all-metal type of stuff may be beneficial. Or applying over a patch panel that is stitched on instead of butt-welded... Or when scupting panels...

So, the added expense doesn't seam justified in my case.

It is interesting to me that those other uses listed would have been places I would have used fiberglass filler years ago. It sounds like these fillers are a modern upgrade to the old fiberglass stuff... is it more water-proof than the fiberglass?