Just tested out my portage rig for my 15lb canoe. It basically consists of an aluminum crossbar that has a couple aluminum angle brackets riveted on the ends. It installs right at the centre of gravity so it balances well.

Other than the crossbar, the other thing I added was lines tied to the first and last rib, these hang down at about waist height so I can grab them and control the tilt of the boat, which is useful for bushwhacking.

The cross bar sits on top of my pack, kind of in a bit of a notch formed between the pack straps and the pack itself.

All in all pretty comfortable, I carried it for about 4.5kms tonight up and down hill and dale, it does put a little more weight on my shoulders than I would prefer, but as its less than 16lbs total for the whole rig it doesn't matter much.

Oh, one downside to it, pretty much everyone looks at you like you are crazy, or calls you Mr Canoehead, which I kind of take as an honor.

Video here:

http://www.youtube.com/watch?v=8kgN8E5bGxY