b. trimble...happy to pass-on what little knowledge is left in my head...btw, i was thinking about the over versus underslung flybar...the high flybar is normally flying in clean air -- except during autorotation and inverted flight, where air flows through the rotor system from the other direction...any rotor blade/paddle will be more efficient in clean air...however, it's more complicated and costly to get the linkages to an upper flybar system...the opposite applies to an underslung flybar...ok -- that's my take on it -- until someone talks me out of it...ken