It depends on how much you need to adjust the trims, as it reads the control position at switch on as being the stick neutral, from which it calculates stick priority. If you change the trims during the flight you alter the neutral compared to what the Cortex thinks is neutral. This will not matter for a little amount of trim but larger amounts would in effect reduce the gain at neutral, and increase then decrease gain as you move the stick in the opposite direction to the trim. It could lead to a slightly wrong value for gain being set. So if you do have to do any substantial trimming during the maiden it's best not to bring the gyro on, then land and cycle the radio on and off for the Cortex to pick up the new neutral position before you start adjusting the gain.

For a first use of a gyro you would never take off with the gyro active as catastrophic mistakes can happen in setting reversed travel direction and/or too much gain. Get to a safe height then gently increase the gain or switch gyro on, and be prepared for immediate switch off if the plane goes out of control. If you switch on and can wiggle the controls and the plane is in control, you are safe to proceed testing the gain value. If you have a reversed gyro control you would get to know about it in a nano-second!