consider a packframe setup - not sure if Knupack is still in business, but its very easy to make your own.  Do a search on here for "knupack" or maybe just "framepack" (modify/expand the standard search parameters ) and you will find several threads, including directions on how to make your own

Advantages -

with a good frame with a good hipbelt, (you can buy one new, or just look at used sporting goods shops)  you can transfer 60% or more of the weight onto your hips, relieveing your shoulders.

with a rope running from bow to stern for "trimming" the angle you want to carry the canoe, you can walk very comfortably, with your arms down at your sides - just pull the stern down to raise the bow, or vice versa, to adjust for the different ups and downs of terrain.

since you don't need to keep your hands on the canoe to keep it balanced, you can carry a paddle in your hand, to be used as a walking stick/balance aid when tracersing mudholes, corduroi, or rocky trials

the canoe rides higher than woth the ususal thwart/yoke, so you can see the trail better ( does make it a little harder to duck under "low bridge" deadfall)

disadvantes - you generally need another person to make loading the canoe onto the frame easier, by holding the bow up high while you duck under the thwart.

you need an "extra" piece of equipment, but some of that extra weight is offset by the fact that you don't need yoke pads on the boat.  


Used to use 69# 15' standard Grummans for years, and that was how we carried them, and would carry them if we used them again.

I like the packframe setup so much that I built a setup for the new Kevlight Northstar, which only weighs 39#, and have a framepack setup for my solo boats as well (more of an issue to load the boat by yourself.)  I find that the comfort and control I have over the boat to be superior to carrying one with a traditional shoulder yoke pad setup.
The heavier the boat, the longer and tougher the portage, the more advantage there is to using the packframe.


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this link will give you a better idea of what I am talking about - I couldn't find the knupack website, so they are probably out of business (they were trying to sell the company, but I don't think they had any
takers)

my rigs are different, in that the "hooks" that the thwart ride in are 4 or 5 inches lower, but similar idea.



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OK, I did find the new knupac website - still under construction - looks like they did find a buyer.