First of all, the only 'rigid' heads that I know of are in the BO-105, BK 117 and Lynx. All others have a version of an articulated head, regardless of what FSI says about th 412 in their stuff. I have also seen a text that says that the AS-350 AStar and Twinstar have rigid rotor heads- not true. The elastomeric bearings in the rotor heads are hinges.
What to call the rotor heads of the Bell 430, MD900/902 and Ec135 is another story- they do not have the high hinge offset that the 'rigid' rotors have, but also do not incorporate any moving parts. I'd think someone would come up with a unique name for them.
Off Level Landings in 'Rigid Rotors'
The preferred method for the Lynx and BO-105 is after the uphill skid is in contact with the ground, leave the cyclic in the middle and lower the collective. You are controlling rolling moment about the uphill skid and the collective is a bigger control than lateral cyclic. Lateral cyclic will induce quite large moments in the mast that eat into the fatigue life. FOr the BO/BK, they put in a mast moment gage. FOr the EX-135, there is a similar gage, but it is buried in the electronic display.