RE: Difficulty trimming for yaw with a CX2.
I had the same issue, but I solved it by modding the transmitter and adding an extra variable resistor pot to the rudder potentiometer. I tuned it so that the yaw is correct with the outside trim at the center. My issue improved after I bought a new swashplate, but my swashplate was all worn off after like 40 flights with 3-cell battery so that is probably not your case.Inspect the motor and the outer bearings though. Exchange the motor functions, move the pinions appropriately and swap connectors to the 4 in 1. If the yaw reverses, it was the motor.