First to get the ballscrews loads within range to each other perform the following procedure.
Return the saddle to its home position, remove the ball nut bolts  from the ballnut housing.
NOTE: The ballscrew closest to the operator/pendant is the master ballscrew, this procedure can be done on either ballscrew. For demonstration purposes the image shows this being done on the master ballscrew.
Mark the position of one of the holes to the ballnut housing with a paint pen and rotate the ballnut  one full revolution until the hole and marking line up again.
Install one of the ballnut bolts back on  making sure to not tighten the ballnut, just get a few threads engaged.
Place a depth gauge on the face of the x-axis ballnut .