Years ago while working in the Adirondacks for SUNY Cortland, we fabricated 50 or so proto-types of these portage packs from old Camp Trails external frames. We used PVC pipe and fittings to create the supports for where the canoe sits. After 25+ years, these are still going out with students on 6 day trips. Each student is fitted to a frame and issued a large dry bag for their gear. The system allows for them to comfortably carry their canoe on one trip across the portage trail and then come back for their pack. The funny thing is a few years after we started doing this, the program was contacted by the company who made the commercial product. They were told we were already doing this with our homemade version and they seemed both impressed and a bit miffed.
That's all for now. Take care and until next time...be well.
snapper