If you use an inverted JVC D-ILA, without a Panamorph,
then the centerline of the lens should be at the same
height as the top of your screen.
Note - this height is independent of the throw distance.
Please note, that if you are projecting 16:9 aspect ratio
images by letterboxing the native 4:3 aspect ratio D-ILA;
the lens aligns with the top of what would be the 4:3 screen.
If you are planning on using a Panamorph, then the window is
set higher since the Panamorph will cause a slightly downward
throw. A rule of thumb is about 5" drop for every 10' of throw -
but use the calculator at the Cygnus Imaging website to get
accurate values. [http://www.cgns.com