I agree with you. Unfortunately I was not rigourous in documenting the effect of each modification individually, and sometimes I made more than one modification at a time.
The differences between movie 1 and movie 2 were:-
C of G moved aft so that the autogyro balanced level when held by rotor spindle.
Rotor mast angle increased from 5 degrees aft to 10 degrees aft.
Rotor blades made more flexible and 3mm x 3mm leading edge spar added. This effectively gave a limited flapping hinge.
Pitch of rotor blades more negative.
With these modifications, I have not noticed any motor torque effects even though I have, on occasion, applied coarse amounts of throttle. The motor, by the way, has 5 degrees of downthrust but no sidethrust. There is now no requirement for lateral trim throughout the speed range.
I feel lucky that we are discussing why the Monotwirl flies well rather than why it flies badly