With a fully articulated rotor, the offset of the flapping hinge exerts a mast moment. When the blades are rotating, they will always try to keep the mast perpendicular with the disk. The greater the offset, the greater the mast moment. This gives you positive control of the fuselage attitude as long as the blades are spinning.
To demonstrate this look at this video.
Griffin Helicopters | Video Player
Even without forward speed the Hughes is almost able to roll over. This is a good demonstration of mast moment gone bad
