To do this, he'd have to be able to take the prop to
significant negative pitch. I'd be surprised if a prop
intended for an airplane would have sufficient negative
adjustment range for this application.

Some of those props had blades with round roots clamped into a
hub, and the blade could be turned all the way around. The Warp Drive
prop is similar.
It occurred to me that the blade's twist would be all wrong for
the wind turbine application, anyway. The blade would have to turn a
lot to get the root to the right angle, and by that time the tip would
be close to feathered, just the opposite of what we need.

Dan