MT
I hate having things in my hands while portaging.  My hands are for grabbing a tree to keep me from falling.
I like the little clip it would be fast to store and retrieve your paddle.  It would be especially good for a rental canoe.  Nothing to mount. I use a similar clip to store my paddles.  My spare bent shaft fits just below the gunnel in the back and does not get in the way while loading or unloading packs. Just sto it and forget it.
Paddle in clips
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To mount the clip on the side of the canoe I mount it on a piece of ¼ inch ply wood with shortened wood screws and then glue the ply wood to the side of the canoe. The glue I use is Goop either plumbers or marine. If you want to remove it grab it with pliers and pull out while slipping a narrow, thin sharp putty knife under it. Then scrub the glue off with scotch bright.
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For my double paddle a clip mounted with a hose clamp on each thwart makes it easy to get in and out.
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The clips are either Harmony/$10 per set or Beckson/$5 per set.  Duckworks also has some folding clips.
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MagicPaddler