How much trouble would it be to add a second sprocket to the freewheel crank? Less than adding extra nylon rollers to keep it in place, I bet. Speaking of nylon rollers, connecting directly to an extra sprocket would eliminate that potential wear problem, and complexity as well. I'd also like to know why it would have to be mounted under the BB, instead of above? I'd pass on the Lithium iron Phosphate battery as well.

Dang, I just dropped a few hundred on another project, so this will have to wait, but I'm chompin' at the bit to build one of these things!