Rear Cab Corner Replacement - Fill with Fiberglass

[dsraven]

'68, that's a nice fitting patch cover you have there. not sure about the expanding foam as it could be a sponge for condensation etc, but was thinking of the patch. could you make it a little bigger and then bend the edges up so it matches the contour of the outside sheet metal? if that were done you could attach the patch to the floor and then use seam sealer around the outside edges to seal the patch from the void and water couldn't find it's way in there but the patch could also be removed easily for access should you need it. another idea I was thinking would be to have some sort of self sealing drain for the void area. much like the ones used on some automotive a/c drains and also off road heavy equipment and farm machinery air filter housings. it is like an extended grommet or rubber tube that fits into the drain hole. the other end of the fitting has been formed flat and has a set of lip like flaps that seal against each other like closed lips but allow internal pressure, like the weight of water, to escape out the lips but seals other things from getting in.
just a thought.