Nice setup complete with auto feathering!
I've gotta agree with Tcmtech you seem to have the blades backwards, as it spins counter-clockwise the leading edge of the blade is a flat surface acting like a big air brake. ...
Your stepper is not a good choice, the 24v is ok but its a 48 step motor, you will get better power and at lower windpeed with a 200 step motor. And those "pressed can" type steppers have much weaker magnets than the more modern NEMA23 size.(