Another ply on the outside will help, but eventually it will get too
heavy.

I'd go the other way. Skin the outside with 1/" wetsuit neoprene.

Really? Don't tease me, I'm an easy target. It's like making fun of Jerry's
kids (Lewis, not Springer) , it just really should be done.

Anybody know where I can get some camo neoprene for cheap?