Aerodynamics are not really the issue when it comes to the scalability of the ABC configuration - its the feasibility of manufacturing a physical rotor head, mast, and blade set that can withstand the exponentially greater loads driven by increases in gross weight, while maintaining overall weight and rotor spacing that keeps drag at a manageable level.
Consider also it is no real mystery why we have not seen any high gross weight conventional rigid rotor helicopters, in spite of the control power and savings in maintenance and component cost (no more hinges, elastomers, bearings, etc) they could provide.
Last edited by SansAnhedral; 26th April 2017 at 21:08.