Can't pin the design yet - but then I don't yet have all of the plans I ordered either. As for the heads, I'd fab new ones with the same size blades, angle of incidence on the blade, etc. as your current setup and use two 4-40 nylon screws through each blade to hold it in place. You can find the screws by Googling on "nylon screw." Why nylon? It will likely shear in the event of a blade strike which will minimize damage to the aircraft. I'd love to take the credit for this one but I believe that it's a feature of Autogyro of Arizona (
http://www.autogyro-rc.com/default.asp ) kits.
As far as not flying, I'm guessing that you mean the flat plate blades. Another peculiarity of twin heads is that they work with flat blades.
- Just don't forget to balance each of your new rotor assemblies.