Used three-inch thick minicell from Kayakoutfitting.com (really speedy service). The footbrace fits solidly against the existing footpegs with no movement. Rather than fill the space between the bulkhead wall and the brace with builders foam, I cut a block of minicell to support the center of the brace. Haven’t decided yet whether to glue the two pieces together. Will probably first try double-sided tape.
The mistake I made was not to take into account that I had to move the footpegs back to accomodate the thickness of the foam, so wound up doing lots of trimming after I had cut the shape (which is why it’s a bit lopsided).
I have a short (12" long) under deck bag which fits nicely in front of the brace, but had to carve out the top of the brace to stash my bilge pump.
Did a one-hour test paddle - felt so much better than using the foot pegs and is great to be able to move my feet around. Even better than a surfski setup. Haven’t yet tried a wet exit to see how it holds up with water in the boat. If need be, I can add some wedges.
What I haven’t done is that 15-degree surface angle discussed in earlier threads. Need at least three or four hours of nonstop paddling to figure that out.
Thanks for all the advice. It’s an amateur job, but hidden.