What about my idea of hand washing the nylon parts with the view to removing all or most of the existing PU coating. Then reapply a new coating, either to the inside or outside, or perhaps both sides. I don't really care about a bit of extra weight. New coating could be diluted silicon or perhaps a spray like Atsko silicon water guard.

Surely something like this is worth a shot? What could I wash it in to remove the PU coating. I could come up with various ways to remove it but I'm asking if anyone has done this before.