The advice I read when setting up my projection system was that your eyes should be ~1/3 from the bottom of the screen. Unfortunately in my setup that wasn't possible (I have a sloped wall on which the screen hangs) and I had to mount it lower.

I can confirm this is less than ideal as it does cause your neck to be uncomfortable after a couple of hours looking at the screen. It's not something you notice immediately, but after 2-3 hours, you realize something's not quite right.

Jason

Epic 80-800: HG Cherry