BBVD,
If you are concerned about packing/ wieght/portability there are other options rather than a framed pontoon boat that will weigh from 25-60 pounds. I have two separate types, the first called a Watermaster and the second is an Escalade made by Scadden craft. Both handle Class III with ease, pack enough gear for multiple night floats, and keep you up out of the water far higher than a tube. Both are also very manueverable with kick fins. I used my Watermaster on the Hoh, Queets and other larger rivers for years without any problems. In addition, I could delfate it, roll up its PVC body and stuff it into a pack with oars that wieghed less than 24 pounds. The Scadden Escalade (which I picked up new for $299 this fall) is more of a kayak shape and weighs only 16 pounds in the pack. Larry Tullis swears by these boats and my friends who use them on the coast since the $299 sale, love them. They are kick butt manuverable, and are a dream to use with fins due to thier shape.

Also, Sierra Trading Post has the Water Skeeter "Pontubes" on sale for pretty cheap right now. They seem like a cool compromise. I've seen them in action on Lenice and Dry Falls. Look like a floating lazy-boy pontoon boat, where the fisher sits way up outa the water. Very light also.
Good luck.