I've been posting and reading other parts of the forum as I was putting together my bike, but recently read old posts here. I see there are quite few about shorter cranks, and more upright riding to relieve back and neck problems. My own issue with a pretty limited range of motion in both hips made me push the limits of bike ergonomics with a really upright riding position, short crank, and electric assist motor on a 20" folding bike.
I'm not quite done but here is what I've done:
I'm using a Sinz Isis 115mm crank (I've also used crank shorteners in the past).
The crank doesn't provide a lot of leverage, and I travel hills to and from work. So I also have a front hub motor (BMC 500W high torque motor that will climb hills), and I put all on an old folding bike with 20" wheels to maximize torque ($40 on Craigslist).
I sit upright and am putting on a 15" stem riser (remember it is a 20" bike). I will use a 1" threaded to 1.125" threadless adapter, make a simple stem riser from the downtube of an old mountain bike, and use a threadless stem. I think it will be plenty strong.
What I really want to try is the Streetstepper stepper bike out of Austria, but it currently seems impossible to get one in the USA.