The Flettner FL282; Transmission plus Flight controls plus Rotor-hubs.
Graviman,
The only possible disadvantage is head clearance...
I assume that you are talking about the low blade tips at the sides. That ain't head clearance. Hell, Herman Goering kicked one of the blades with his boot.
The
Flettner FL282 had an angle of 24-deg between the two masts.
Kellett wanted to go to 3-bladed rotors with greater rigidity, however lack of funding and his demise ended that endeavor.
Extremely rigid rotors result in a smaller angle between the two masts, plus no blade droop. The blade at 90-deg azimuth on the
proposed wide stagger UniCopter actually has a positive angle of 1-deg.
Dave