Effeciency vs. weight/complexity? I would think CR props only become economical when you are talking huge engines like the bear. How big/how many blades of a conventional prop would you need on a Bear with engines that big?
Ailerons 'deflecting' the slip-stream? I was taught that the downward aileron increased the angle of attack of the wing and increased the lift of that wing while the 'upward' aileron deflected the slipstream.