Finally had a few extra minutes so I screwed the two screens to a 2x4 exactly 12 inches apart. I set the dials inside the unit to "0" and "1", which tells it 1ft apart, and tested it with a BB gun in my backyard. And it worked For such an old piece of equipment I was pretty surprised. Not only did it work, but it tells you the ES, SD, hi, and low after you're done shooting. It seemed to work fine without any diffusers. Do I really need to buy some? What would the benifit be? I'm considering canceling my M35 order now and maybe buying some SSIII screens for this unit. They come with diffusers. Oh ya, and before I forget to say it, no, the units was not sitting right next to the screens when I took my shots. I made sure it was real far away. I just put it there for the picture.