If you really want to gain some wait, I recommend Septic Shock! With the tube hydrating my I was able to add 40 pounds. Unfortunately, afterwards you'll pee most of it off, but you can live the dream of bloat for a while.
There are limited areas with rock (Sawtooth Ridge or the Needles and a few other places) that is of quality that really allows "rock climbing" (and the rock in the Olympics is complete choss compared to granite found in the Cascades), but if you're looking for 3-4th class scrambles that are tons of places. Get a copy of the Oly Mtn Guide and sift through the TRs here...and of course it is hard to go wrong with just going exploring out there on your own.