I like JanSport external frame pack very much, although shortcomings exist. It is easy to improve and remodel. The new Carson 80 have many advantages than older model. The hip-belt and shoulder-belts were re-designed and fit well, but slightly harder than before. The size of external frame is smaller than the old D3 frame, but it is too large, because I am living in Japan and Japanese mountains are steep. So, I had completely re-modeled Carson 80. In the first place, I had cut the frame shorter and attached the old D3 joints to the frame. In the second, I twisted the hinge to fit my waist and sewed the used insole to the belt, because it was too solid. I also changed the way of connecting shoulder yoke to slant easily and fit well. And I change the way of passing the belts, because the buckles easily loosen. I cannot upload other photos. Please see my HP. http://psycho01.edu.u-toyama.ac.jp/carson80.html
Recently, I purchased these crampons for my wife. The snow gorge freezes in the morning even in the summer time (Japan). These crampons are fitted well for my wifes shoes and very light. I also cut the size adjustable sticks and belts a little shorter, and these came -18 gram weight loss. Thinking about safety, these crampons are excelent.
The frame is very rigid and flexible, all the loads hang to both sides of the waist. I walked throuth the Northan Alps in Japan for five days, started with 22Kg load. I recommend this pack for serious backpacker who walks steeper mountains with heavy load. This is a
revolutionaly designed backpack. To our regret, the agency in Japan doesn't sell. So, I recommend this pack in my HP (http://psycho01.edu.u-toyama.ac.jp)