Yep you got it Robbo,
If both rotor systems are producing torque - 1 cancelling/opposing the other you will be able to effect yaw control by pedals either
1. Slight tilt of one disc fwd while the other back .
2. Slight pitch inc in one disc + dec in the other ....... therefore different/uneven torque, a/c will turn with the larger torque reaction.
or a mix of both.
mmmmmmm 1/2 bottle of very nice chardonnay followed by a "stonking" coffee. Luverly mix! I recommend it!!
Now I just need somewhere warm and soft to curl up.
G'night