If I may add, I believe that with speed controllers, one for...

If I may add, I believe that with speed controllers, one for each motor the speed of each motor can be varied individually so as to turn on a point. The weight of the roam-e hanging below the blades will act as vertical stabiliser. That's my understanding as( don't laugh) I was going to build a flying saucer model once using this principle but with enclosed blades. At the time the contra- rotating device was not available in miniture for models. I know it is now though. We are talking 20 years ago. Really look forward to examining the mechanism close up when I all being well get one. GLTAH today. Bring on .10c +