Thank you for the insight/thoughts!
They are fixed. After I glued the two pieces of (closed cell I believe?) foam and wood block together, I then stretched the faux leather around and used about a dozen staples to secure. I then attached it to the metal bracket with screws, sticking with the shape/template of the metal. Hoping the general shape/placement proves somewhat universal, but to your point, I should be fully prepared to go back to drawing board.
Your setup/canoe looks real slick (and light! My body tells me to move on from the Grummans after some longer portages, in due time I'm sure it will happen. Glutton for punishment I guess)
I take with your setup you have a little wiggle room to loosen the bracket and slide it back or forth (if needed)? I like that