Lu,
I don't disagree with your remarks about the propeller.
Previously mentioned was, " For gyroscopic precession to take place, the rotating device must have considerable [Angular Momentum]. A helicopter's rotor does not have enough."
This [Angular momentum] involves RPM and mass. A propeller has a much higher RPM and, proportionately, a much higher mass than the helicopter rotor.
______________
I actually hope that the UniCopter's two counterrotating rigid rotors do exhibit
a little gyroscopic precession. This is desired to give the craft dynamic stability in pitch and roll.
Counterrotating Gyroscopes (Dynamic Stability):
Assume that the rotational part of a gyroscope is mounted on a stationary vertical axle. Assume, also, that we are looking down at the gyroscope (plan view) and that the locations of interest are the four primary points of the compass.
If the gyroscope was rotated CW an upward force on the West will cause the North to rise and the South to lower, due to precession. If the gyroscope was then rotated CCW the same upward force on the West will now cause the South to rise and the North to lower.
If we put two counterrotating gyroscopes on the same rigid axle and again apply an upward force on the West the opposing North and South forces will cancel each other. The axle can freely yaw but there is resistance to pitch and to roll.
_____________
If you want to pursue gyroscopic precession further, we should go to the [Gyroscopic Precession - Revisited] thread, so that other can beat up on you, also.
Now to tackle your main point.
Dave J