Looking forward to this thread, I have just started researching the same issue. Mid drive is definitely the way to go for tandem hill climbing. Blade-Runner, is it true that left side drive is the only way to mount to the captain BB? I was hoping that the torque would be transmitted through the axle, so that I could use a conventional kit and just put my leftside chainring-crank on. The right hand chainring would not be connected to anything.