Whilst the gyro operates in AVCS mode the tail pitch is entirely controlled by the gyro. In this mode the pilot’s rudder inputs become a command for the gyro telling it how fast to yaw; the gyro then controls the tail pitch as needed to maintain the commanded yaw rate. Adjusting the transmitter endpoint will only affect the speed the heli yaws at full stick - it does not affect how much the servo travels. The servo endpoints must be adjusted on the gyro as the gyro controls the servo and as such the gyro needs to know where the travel limits for the servo are.