I just completed an SOF 'Adirondak pack canoe' based (loosely) on Rushton's Nessmuk designs.

loa 11' 10"
max beam 26"
depth at center 10.5"
total weight 22 pounds

It is a bit heavier than necessary, (I could easily drop 10% if I build a second) but great to handle both on and off the water. Cruises pretty comfortably at 3 to 3.5 mph with a double paddle, I can sprint it up to 5 mph (for maybe a minute)
it handles my 175# plus 35# of gear nicely.

I would strongly suggest that you not drop much below 12' oal, or else it will be difficult to get your displacement. if you get too beamy, the double paddle gets tough to use.