I love the simplicity of that design, Ed ,a 2x8, couple of
bolts, & some wheels. That would,(with a few mods), make a reasonable
chasis for a velo tadpole. I could see using corrugated plastic sheet
to form the shell.
Yesterday at the hardware store there was a gal with an electric
tadpole trike with a 2800 watt crystalite motor. That's almost 4 hp.
with instant torque. As low as it was, I'll wager it could do 50+
with a shell.