Nick,
To my knowledge, 'Principles of Helicopter Aerodynamics' by Leishman (University of Maryland) is the latest Western book (2000) on rotorcraft aerodynamics. Few people, if any, would dispute his competence.
On page 224 he says
"Roughly, the tail rotor consumes up to about 10% of the total aircraft power. This power is completely lost, because unless the tail rotor is canted, as on the UH-60 Blackhawk, it provides no useful lifting force."
In another section of the book he remarks that earlier Western aerodynamist had under estimated the power consumed by a tail rotor.
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Chose something to bear in mind:
OK.
"What went so wrong and why has there been sixty years of tail-rotor dominance? At the risk of irritating some, I suggest that the Germans, plus the Russians and the Europeans lost the Second World War, economically, whereas the United States was the major winner. The ideas that were prevalent in the United States at that time became the predominant configuration. The majority and the financially endowed went with the single rotor, and 'simply' offset its torque with a horizontal fan. I suspect that the problems confronting the rotor aerodynamists were formidable and the early American developers resisted compounding these problems by having to deal with two main rotors. Unfortunately, this configuration with a tail rotor created a new set of problems that can never be adequately overcome."
Dave