Hi again,
then maybe it has a general cause, so let's try fixing it by concentrating on one heli.
In general, tail authority depends on
. head speed / tail rotor speed
. length and airfoil of the tail blades
. maximum tail pitch (but not too much either, a stall would also cause such effects)
. the servo itself, it's linkage, symmetry, travel (length of servo arm – sounds OK as described OK)
. the tail linkage (free of play, smooth)
When the mechanical setup is OK, you would first do the optimizer flight (for each head speed/bank), this will equalize the stop behavior as good as possible.
Once that is done, you have a reference on how strong your tail is: low optimizer values, strong tail, high values, weak tail. It will be different with and against the torque, obviously.
Then, you can use the stop gain values to equalize even more. Depending on the givens, it can be necessary to soften the stronger direction a bit, to meet the maximum in the weaker direction.
You can also try lowering I (integrator, heading hold) and/or increasing P (proportional), or add some D (differential).
But only one at a time, to compare, and always leave one bank as a safe bank, so if you run into troubles, e.g. hard oscillation, you can always switch back.
On scale helis as well as on very small helis, it can be necessary to decrease Acceleration (delay in vintage-gyro-speak, but reversed), to leave the model more time to react.
Best,
Eddi
Born to fly ...
forced to work.