I have a DaLite model B with CSR. The question you ask is a good one. The model B has stops in its travel about every 4-6 inches, so when you pull it down, you can get it to stop in the same place every time. The issue is how you set up the projector with the screen. The projector must throw an image that is perfectly aligned with one of these stops, or the screen will not show the entire image. I have a Z1 with lens shift capability, so I mounted the projector first (roughly in the right place for the height I wished) and then simply shifted the lens up and down to match the screen stop that was closest to my desired height. Without the ability to shift the lens, you would have to move the projector to match the screen, or mount the screen first and then measure very carefully to get the height right when you mount the projector.
Once it is all set up, it is simply a matter of pulling down the screen to the same place every time. It's no problem.