Progress. I first marked 3/4" steps on the plywood for the rudder peddles, then mixed up some thickened epoxy.
I strung the carbon tubing segments along a drinking straw, applied dabs of epoxy and then attached the carbon-tubes, holding everything in place with
blue masking tape. This operation was so neat I was able to slide out the straws and use them to make matching tubes on the footrest.
These pin tubes are lined up well.
The carbon tubes seem incredibly strong, yet with the 3/4" lengths, twice they've crushed longitudinally.

Next step is to wrap them in carbon fiber and build up some layers. On one of my failed attempts I cut the carbon fiber on the bias (diagonally), it just fell apart.
This time I think I will begin by carefully making sure I cut along a thread so I have a grid.

The rubber idea sounds feasible. How well does rubber hold up around salt water?
One important issue for me as an ocean going kayaker going on 3-5 hour off shore paddles is when something fails, is it going to happen 9 miles off the coast?
That's what happen to my Smarttrack pegs, more than once. A little pin used to work its way out--always far off the coast, or a mile off Anacapa Island.
If the rubber could be expected to last, say two years, I should replace it every year.

Layer build up requiring deepening the notch between the 'tubes' of the hinge. This is true of all hinges. All require a deeper notch to accommodate the thickness
of the hinge material. A rough file should work.
Because the hinge doesn't need to move more than 30 degrees I think I'll toughen up the backing.
I'll put up some photos when I've got something I'm confident will work.