In my case I find that I must first zero out any lens shift as a starting point. Which is what Ron is saying. One way to do that is to turn the projector on and then center the light exiting through the lens in the exact center of the lens. Then the projector can be leveled in the mount and then lens shift dialed in if necessary. The best part, the sweet spot if you will, of almost any lens is the exact center. But necessity trumps perfection at times.