The Gyrodyne had tip brakes; -vanes that pop out of blade tips to increase the drag on one or the other rotor for yaw control.Kaman still uses servo flaps on their intermesher ..... but I think if you look up the coaxial Gyrodyne drones from years back ... they may have used flaps .... I could be wrong ... going by memory.
Thanks for the link, so from the information on the link, best for lower power is two side by side rotor systems and best stability is intermeshing, then coaxial?
Dave passed away in 2017.... I wish he had arranged to preserve his website .... tons of good info he gathered over many years.Hey Dave, you still around?