I made a little video on how I adjusted my motors on my mill with the Gecko G540. I'm sure there are other ways to do this but this way worked for me.
This is a not the newest G540 that has the pots close to the cover. I would guess that they would adjust the same way only easier to find the screws.
I hope someone finds this useful.
http://youtu.be/7EEXFu1beHI