If it were yours, what would you do (floor pans)

[89 MJ]

I would sand all of the rust off and then hit it with something like a weld through primer. Though if you want to go with the panel bond method, which is equally as good, if not better, then just sand all of the rust off and glue the new panels in.

[A-man930]

Remember that, after this is all done, you should apply a cavity wax and some kind of lanolin-based undercoat like FluidFilm or Surface Shield.  The undercoat does have to be periodically reapplied in high wear areas, but it does seem to be the ultimate final step in Rust prevention.