As I understand it, there is a direct correlation between an offset hinge dimension and the phase lag angle. The great the offset hinge dimension (distance between center of the mast and flapping hinge) the smaller the phase lag angle (i.e. < 90). This is because the offset increases the speed at which the blade arrives at the desired flap angle.
It appears that the Robinson's flapping/coning hinges cannot be considered as conventional flapping hinges because the teetering hinge negates the effect of the offset.
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The following modification to the Robinson rotor head is suggested, with tongue in cheek.
The two grips be geared together so that they cone in unison. This linked coning will still compensate for the 'lightness' of the blades, while also removing any tendency for these hinges to flap. The pitch horns can then be extended so that the phase angle is 90-degrees and the pitch link is vertical.
The only modification left is to relocate the pitch horns and links at the trailing edge of the blades. Now the rotor will act like a conventional teetering rotor, except that when the blades cone some of their pitch will be pulled out.
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For those that might be interested, the following web page contains Frank Robinson's Nov/2000 posting on this conference.
http://www.synchrolite.com/B185.html#Robinson