Just as an aside, I stopped and talked to some of these urban boatbuilder kids in the BWCA last August who had built the boats they were in. I personally would have no problem using a skin on frame boat for lake/portage trips, but would be a little more careful than normal. I've built a skin on frame kayak and am surprised how tough it is. I mounted a sheet of the nylon fabric on an old seat frame and put the same urethane coating on it to test its strength. I should have video taped my efforts at puncturing the skin. I could do it with a sharp knife, but a screwdriver pretty much just bounced off. I would say that these boats are probably the most susceptible to damage when not in the water, like when you're portaging and you trip and the boat goes flying into a stump or big rock. It's the wood frame itself that would be my biggest concern, but it would all be easy to repair in the field anyway with some artificial sinew and a bit of wood lying on the ground. Similar to any boat, long term abrasion would be another problem that can probably be taken care of with the addition of some type of skid plates.
Back to the kids, they all looked like urban kids and unfortunately were headed to a really long portage with only an hour of sunlight left with big storm clouds approaching. I can remember thinking to myself that they are in for a lesson today. Later, while hanging out under my tarp, I was thinking there's no way they made it to the other end with all their stuff before dark.
Mark