Variable pitch gives instant thrust change where there will be a delay with variable speed as the tail rotor accelerates or decelerates. Having flown fixed pitch and collective pitch RC helicopters I can tell you there is a big difference in the controllability of the two. Many times the simplest mechanical solution is not the best answer to the problem, especially where pilot control feel is involved.Great fotos!
Looks very simple, and he only take atvantage of half of it - he still use variable pitch!?