I've had an idea.....
If you take a folding R20 and unbolt the joint so you have a front and back part.
Take a "spine" that is a length of (probably rectangular section) tube, and bolt the front and back parts of the bike onto the "spine"
You now have a long wheelbase R20.
If the spine:
* has at the front end a bottom bracket with pedals and chain ring
* has at the back end a seat (purple bit)
*has in the middle a "headset" with handle bars
you can remove the R20 seat, remove the R20 handlebars and replace with a stub steerer tube with a little side tab on.
The steerer on the spine headset is connected to the stub steerer in the forks by a rod linkage (red line)
The R20 pedals and cranks are removed and a modified (crank arm is sawn off) is bolted on.
The spine pedals are connected to one of the double sprockets on the original R20 bottom bracket by a chain. The other sprocket on the R20 bottom bracket connects to the rear hub as per normal.
Brakes and gears rerouted to the new spine handle bars.
I give you the R20cumbent bike (R20bent for short)
Comments, abuse, praise, donations etc all welcome!