Thank you all,
I'm trying something similar to Paul's method.
It seems kinda of obvious now.
I cut short lengths of the carbon tubing, mixed up a tiny amount of thickened epoxy; on edges of the 1/8" plywood I put a dab at the location of each of the three 3/4" lengths of tubing. The tubing was taped to a drinking straw at the proper spacing, pressed on and taped to the edge.
I set them in place. Should work.

My mistake was to attempt two steps in one. The next step will be to wrap carbon fiber over the short pieces of tubing to firmly attach them to the
peddles. If this works then I'll do the same to main footplate (which already has two layers of carbon)

I need to make sturdy blocks to slide in the anodized aluminum channel to make a firm connection to my kayak hull.
The legs of most of us can lift (on a press machine) 600--900 pounds (250 --400 kg), half of that per leg. I'm amazed that kayak pegs hold up as well as they do.
I'm also wondering whose idea it was to use 'pegs'. I'd like to meet the guy and make him stand on a piece of pipe for a couple of hours.

Will

: Forget trying to make slots of your carbon fiber. Buy a carbon
: fiber tube, cut it into short lengths ( about an inch or so,
: shove a stainless bolt or heavy wire inside to keep the parts in
: alignment and close together, and glass that, (or use carbon
: cloth) onto your pedal setup.

: Just use a few drops of hotmelt glue or fast setting epoxy to hold
: the hinge in place. once that has set, pull the pin and do a
: full strength job aon all the joints

: PGJ