Basicly Curt needs a set-up which is also used for bicycling on trikes and on stationary bikes with active/ passive electric motion enhancement.
could make a test version out of a gallon-size container which is cut diagonally in half.
The lower part is then bolted to the pedal (using wingnuts), longer bots could hold a counter weight to keep the cradle the right side up and/or make an attachment point for a bungee cord leading in the bow direction, by tensioning this cord it helps pulling the left arm of the MD forward to assist Curt`s left leg.
Cutting board (Kitchen utensil) is easily tooled to make a backing plate in the foot cradle.
Round of carefully, sensory loss is common, so wear neoprene booties.
For the rudder control, if shoulder movement is better, I would go for a rounded PVC gutter where Curt`s forearm is resting in,
Could be attached to an U shaped SS proflie which covers the handle and is connected with one bolt going through both the profile and the tumb area of the handle.
Between the profile and the gutter 2 rubber joints like the ones used in windsurfing heighten the gutter and makes it a flexible construction.
Can post a piccie after tomorrow`s workday of a foot cradle on a recumbent
Also saw this a while ago