Ahoy!
Here's some info on the interior walls on the E-37...I just had to replace the wall material along the outside walls of the boat, behind the bookshelves and quarterberths due to years of leaky chainplates and condensation. What Endeavour used was 1/8" plywood paneling with vinyl wallpaper glued to it. It did not appear to be any kind of "marine grade" stuff (my boat was made without all the stripy-looking horizontal teak strips). As a side note, the ceiling panels are just naugahyde stretched over ordinary exterior grade plywood, not marine ply. On ripping the old wall material out, I found that it had been attached haphazardly with glue along the bottom, and a couple of non-stainless screws along the top to a sort of "spacer" board consisting of a strip of scrap 1" plywood that was not fastened to anything!
To replace this wall material, I have selected a plastic sheeting called Komatex, which is available in white and several colors, in various thicknesses. It is flexible, easy to cut with a saw or packing knife, can be screwed, glued, painted, etc. , and is available from most plastic supply houses. I re-attached or replaced the Spacer boards by screwing them directly to the hull with 1 1/4" stainless screws (had to be careful not to drill all the way thru, but the hull is pretty thick there). They are needed as the hull takes a sharp turn inward a few inches up from the bookshelves...I think there is a stringer of some sort in there.
Then I cut the Komatex to fit with a packing knife, using the 1/8" thickness in Flat White. In order to fit it properly, it was also necessary to remove the ceiling panels, and so I discovered a couple of leaky stanchion bases also, and could fix those. Then I laid a bead of silicone adhesive along the bottom, behind the teak trim strip, and put in the new panels. I also had wanted some insulation, so I glued some thin foam board in behind the new panels, using exterior grade Liquid Nails. Now the walls are neat, clean and white, and can't rot even if I get more leaking. As I have moved the chainplates outboard (another big project!) I don't anticipate much problem leaking from them, but I did leave access holes in the Komatex where the chainplate bolts are, with little screw-down Komatex pieces to cover.
You may be interested to note that the Stanchion bases, if you have never looked, are reinforced with some pretty good 1/4" aluminum backing plates and some smaller backing plates on top of THOSE.