You can change the homing/limit location to whatever you want (i.e. X= +120.000"). Within the Homing/Limits dialogue, there is a setting for homing negative.
Another option would be to reverse the X axis AND Y axis motor outputs. I think this is done with the direction signal (active low or active high).
Disclaimer!!! I have been awake for 36 hours. Will someone come along and educate us both?