The other reason you don't need a lot of power to the tail during autorotation is that you don't have to overcome the torque of the main rotor. A smallish battery would be enough.
I completely understand PilotDAR's point about thinking about certification throughout the design process, but there's still a big difference between discussing innovations that obey the laws of physics and those that don't.
Last edited by abgd; 3rd Dec 2018 at 23:15.