The very first e-bike I ever built-- back in the 1990s-- used a Softride beam. I made the frame for the job, from a section of teardrop cross-section sailboat mast. Thirty Sanyo NiCd D cells were stuffed up into the frame boom. The front wheel was a flat carbon disc with a GaAs photovoltaic array on it, and the rear wheel was laced to an 800W Heinzmann hub motor. I used a 700C Manitou suspension fork, when that was a very exotic item.
Instead of putting batteries in the space under the Softride beam, there was a second GaAs photovoltaic array on a carbon/Kevlar layup. Combined, the two panels provided 100W of charging power in full Texas sun.
The guy I built the bike for was intent on having all that high tech stuff. At the time, I didn't think an electric bike would ever be something I wanted for myself.