Thank you for the explanation.
That does explain the large separation of the two rotor systems on the Kamov as compared to the much smaller vertical separation of the ABC system.
Knowing the Rigid Rotor system is only on the BO and BK did not strike me as notable but in light of what you describe it does make sense. The BK is a derivative of the BO and not much increase in size. I have never heard a conversation about why those are the only two "Rigid Rotor" aircraft.
Sizing of Rotor Systems....diameter, blade chord, and numbers of blades has always seemed a Black Art of sorts....then compound that by adding a second set of Blades and I can see how complex it all becomes.
The Sikorsky ABC competed with the Bell Tilt Rotor back in the early 80's in an Army Test Program....with the ABC concept not getting the Nod.... which resulted with the advent of the V-22 Program.
Did the possible shortcomings of the ABC Concept, as you are describing now, become factors that led to the Tilt Rotor concept gaining acceptance by the Military and the ABC not?