Danno,
I followed Dustin's excellent video to set up my gyros on my 12x using either their own switch, or flight modes. The video is for the JR 370A, but can be applied to pretty much any gyro that uses a gain channel. So far, I've set up an Eagletree Guardian, BlueLight Iceman and two Cortex gyros using the methods described.
For fine tuning, I assign the gain channel to the left slider first. Once I'm happy with the gain setting, I then change the gain channel to the gyro sens as Dustin describes and transfer the gain setting to the gyro sens.
https://www.youtube.com/watch?v=fpp7tjJGH_Y
The nice thing about using this with flight modes is that you can have five different gain settings, each attached to a specific flight mode.
Have fun!
...jim