Robin,
I have repaired soggy core on my Ariel, including removing six feet of the outer skin on the port side deck, replacing the core, and and reattaching the skin. Of course, it requires cosmetic glass work and repainting the whole deck including determining how you will restore the non-skid (I used glass beads).
I'm happy to tell you how I did it, and have a few pictures, if you're interested.
--Dave Gillespie