The WW boat I've been using at roll class has an interesting footbrace arrangement. It looks kind of like a back band in reverse. There are 2 studs mounted on each side of the cockpit at the waterline just about even with your knee. A long piece of 3/16" x 1.5" aluminum flat bar is bent in a deep "u" shape. the foot brace is mounted at the bottom end of the "u". The tails are drilled with multiple holes to fit the double studs. To adjust, you remove the wing nuts and switch holes. Not as easy to adjust as a slider but, it can't flop around in a roll or during re-entry.
The foot brace is sized to fit the profile of the boot at the furthest forward position. You could mount the brace at an angle to suit your comfort. Adapting for a rudder could be a problem.

: I haven't found any pegs that are adjustable that I really like. I ended up
: changing my OuterIsland to what I can only describe as an angled bulkhead.
: I made up a piece of plywood that is mounted down from the deck about 2-3
: inches, against the forward bulkhead and angles back toward your heels.
: With it mounted at an angle it gives better feel and more room for toes.

: After going hog wild on the Greenland bug, I found I really like the ability
: of being able to place your foot in different locations across the boat.
: Something you can't do with pegs. I also found my feet slipping off the
: pegs during some of the different rolls. This is prevented by having the
: large area for your feet with the bulkhead approach.

: The draw back is the boat only fits you or people your size.