Perhaps think it through some more?
Regarding the possible range of pitching moments (+, 0, - ) we're discussing a continuum, not either/or behavior.
+x Cmo pitches up and adds to blowback effect
with AS, cyclic flapping angle greatly increases, and stick moves forward to the stop
0 Cmo is neutral in pitch
with AS, cyclic flapping angle moderately increases (due to blowback effect), and stick moves somewhat forward
-x Cmo pitches down and counteracts (to y degree) blowback effect
with AS, cyclic flapping angle (depending on -x and construction of blade) either does not increase or decreases, stick has little movement
What I've postulated all along is a small amount of negative Cmo in a rigid blade is not inherently "dangerous"
because the blowback effect is not completely overwhelmed.
Now, I'm not claiming that the relationship between -Cmo and blowback is 1:1 over all airspeeds, but given the well-known
Sport Copter performance amongst hundreds of machines, their lack of "stick moving back with AS" is clear evidence
that Vanek's -Cmo airfoil enjoys rather a just-enough-but-not-excessively "sweet spot" in countering blowback effect .
I.e., if the SC stick does not routinely shift aft with increasing AS, that means that the cyclic flapping angle is remaining pretty constant.
Thus, there is much less need to re-trim for cruise airspeeds.
In short, at cruise there is a rough equilibrium between blowback effect and negative pitching moment.
While the data curves of each force do not perfectly overlap, there's apparently good overlap in a wide range of cruise AS.
Think "continuum" and it'll make sense.
If Chuck wishes to continue to assert that any -Cmo will at "some airspeed" cause the gyro to descend beyond cyclic authority of correction,
then he should quote that airspeed. If, as I suspect, it is so high (e.g. 185kts, a multiple of the gyro's Vne, and thus silly), then realistically his accusation is baseless.
If that AS were <Vne, then he'd have an actual point here, but it's a broad brush boogeyman.
As I mentioned, Jim Vanek has tested his airfoil in a dive at 145mph, which was obviously not unrecoverable since no crash ensued.
And, really, can anyone actually imagine that Jim would be selling rotors which were notorious for continual aft stick with airspeed?
I'm aware of zero crashes of any Sport Copter due to deficiencies in materials or design.
How's that for "stability", fara?
Regards, Kolibri