This is pretty simple and could be easily adapted to a canoe.

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One thing he mentions is that with Paracord, you get line slack when wet and to taut when dry other times?
I think I would opt for some of that guy line cord I bought from Cooke's Sewing or similar for set-up.

I know from using it on my Dry-Fly and Pack hanging rig that it doesn't stretch when wet and is more than strong enough.