2 bladed machines have a vibration mode that is mostly vertical (because blade pass the front and back location in tandem at the same time, front and back being where most the lift is generated)
3 blade machines have some lateral vibration moment for that same reason (blade do not pass the high lift azimut in tandem) Therefore 3 blade machine like the astar (AS350) have a mass spring system in the rotor head hub to cancel out that sideways vibration moment
the R44 long rotor mast might be ill equipped to receive
1/ lateral vibration moment
2/ torsional moment of a rigid rotor head
remember an articulated rotor head wants to pull the fuselage in a new direction thus changing the attitude
a rigid rotor head wants to apply moment on the rotor shaft to force the fuselage into a new attitude
Then if you I think about the Enstrom long mast and 3 bladed head, it seems to be technically viable.