Nothing wrong with using a frame pack if that works for you.  I always have a packframe with me for portaging the canoe.  For longer portages, I'll just lash my duffle bag to the frame (takes about 60 seconds, if that), hook the shoulder straps of my dayback on the top corners, and use that for the portage. Fitting a fram into the canoe may be an issue - but I've never really had any problems doing it.