You can check the dish by simply flipping the wheel in the stand.

I'd purchased a used 2.2 that was out of center.
I struggled with attempting to center it myself, but could only get it to center on one OL width at a time. Switch from say a 100 to 135mm and it was off.
I downloaded the centering instructions from PARK and followed them.
It's DEAD ON! First attempt. I might have got a little lucky?