For my diploma work, that was completed more than a year ago, i used a AB-412 for a test flight. First test was the smoke grenade, the second was measuring the direction and velocity of the air stream while on the hoist. Here are is a photo from that day.
And the solution from my point of view, a little big, but later i corrected it to about half it's size, to still perform its function as a pasive counteract against spinning. Active stearing system was proven by french, with a movable flap on one end of the strecher. They had proven that it can be done, even more... very controlable.
