I did a maiden a few weeks ago that had the cortex in heading hold and I had a real hard time flying it. It was a wrestling match lol. But after a few laps trying to trim it out and fighting it I figured it out and turned it off and finished trimming the model out and landed ok. I got in a hurry and forgot to check this before the first flight. Normally I disable the heading hold when I first install the gyro since I will never used it.