About six years ago, I built tenor ukulele that was to live full-time on a small sailboat mostly in the tropics. This is a difficult environment because of humidity swings and the certainty that everything on a small boat gets wet from time to time. It has done just fine. The body was built conventionally out of mahogany and coated inside and out with this penetrating epoxy before finishing with a polymerizing oil:
http://www.smithandcompany.org/CPES/index.html
Someone might howl that this treatment changes the tonal properties of the wood but that effect, if present at all, was not detectable by me. In truth, the epoxy doesn't penetrate sound wood much at all, except perhaps into end grain, but it does saturate and seal the surface of the wood. In any event, this method certainly meets an aesthetic goal that HPL never will.