Been working on my own interpretation, which I call my "Armchair Truck". It has been fun designing it - seat height is 10" at the leading edge, seat back is intended to be adjustable through a small angle change. Decided, in the interests of having a decent turning radius and still only a 30" wide wheelbase, to use 16" wheels on the front. Since I need centralized steering I went with a tiller raked at 20 degrees, same as the front forks, to a swing arm/tie rod arrangement just under the seat. I have some screen captures from the sketching process, with various details still to be filled in, but I'll have to post those later, after trimming/resizing. Modelling that folding top in SketchUp has proven to be beyond my skills - the frame I can do, but the fabric surfaces are much more difficult.