I figure that if I once measure how far the arm on the spindle needs to move to go lock to lock, - then I can make the arm for the box that will give me the corresponding throw. It may take some experimentation. One of the concerns is that a ratio that is too fast would take too much effort to turn.
With that butterfly wheel I'd like to keep the number of rotations to a minimum but I'm also concerned about a ratio that would be so touchy that minor movements would cause an oversteer.