Hi Gyronut !!! The reason no one is using the 2-bladed teeter head (in R/C model form) is because it hasn't been perfected yet. They say that necessity is the mother of all invention, so what better reason to finally develop a two bladed head ?? I guess it will be left for open-minded experimenters like me to cut-and-try until success has been achieved. By the way, Juan De La Cierva did not have a wind tunnel but still managed to produce a successful autogiro. Wind tunnels are not needed. All that is needed is some good ol' fashioned American ingenuity, a basic understanding of what makes a teeter head work, and the guts to go where no man has gone before. I will undertake this challenge, and prove to the many nay-sayers that it is not only possible, but is preferable to the semi-rigid flex plate rotor head. Anyone else out there up to the challenge ?? Remember, No guts, No Glory !!! Charlie Anderson