Max, the underslung design refers to the fact that the teetering hinge is located in a higher position than the blades rotating plane.
The whole rotor hub assembly teeters as one, this to allow for flapping motion. At low rotor RPMs or extreme low Gs manouvering, the flapping motion can exceed its static limits and cause the rotor hub tio contact the mast with consequences as severe as severing it.
The typical Bell two blades rotor system is considered a semirigid one.
When you mentioned the V-22 didn't you really mean the R-22? But then you mentioned negative Gs so it has to be the V-22.