Most of my trips are in a 22lb ultralight pack canoe that sits very lightly on my shoulders/packstraps when the dis-assembled double paddle is used as a yoke.
But if I portaged a traditional tandem canoe, yeah maybe... the KnuPack was the former solution. But the pack must solve both problems; portaging AND being a well-made, practical bag.
In my experience, frame packs don't fit well in canoes... there's always something sticking out somewhere that's in the way. This is why the traditional canoe packs are simply soft bags with shoulder and head straps.... they just 'fit' wherever you have to stash them.
Personally, I prefer a sack with no internal compartments or extras (like a 'hydration system hanger' or 'hose outlet'; these are merely extra dead weight.) A waist strap is helpful if the load is over 25lbs, which it probably would be in this case. There MUST be 3 external pockets: one on each side capable of holding a 1qt Gatorade bottle plus a sneaker/hiking shoe, about 14-15" deep, with a roller-buckled flap and drainage grommet in the bottom, and 'pass-through' space behind it (like a Bergen's Norwegian army pack), and one larger central pocket for use as a 'junk drawer', with two high quality ROLLER buckles.
I'd also like that pack to have a flap with LONG straps, like a traditional portage pack, so you can stick your life jacket and rain gear under it easily. That flap also needs to be two-layered, with a velcro seal along the lower edge, for maps. If you couldn't do the pass-behind pockets (for axes), then an axe loop under the flap might be useful, but you can always just tie the ax/hatchet to the frame, especially if you do 2x side straps over each pocket.
The frame needs no real explanation, but the shoulder straps MUST be able to be adjusted, not just in length, but from dead center outwards. Look at the Bergen's, and look at a 19th century/early 20th century soldier's pack. Notice how the Bergen's comes from the middle (properly), and the soldier's packs generally pull the bejesus out of your shoulders because they are set too widely apart. Most European military web gear, and the old US Alice system, works like this; it's called a Y harness. The H harness hurts.
I personally would prefer it all in leather/canvas, not nylon. Pack capacity in my case would need to be about 60-70L.
You might also survey folks on whether or not they wanted a frame-mounted dry bag with a roll top, like the SealLine Black Canyon. Personally think that would be too heavy (probably 6-7lbs).
Just for comparison, I use an old Go Lite Gust (22oz) with a 25L dry bag inside (12oz) for a total pack weight of just over 2lbs... my total weight of gear and food for 5-6 days is about 55-60lbs, including my worn clothing, gear to include saw and hatchet, pack, canoe, fishing gear, and rubber boots. Not willing to add 3-5 more lbs to that just for a frame and bag.
