-- You don't have to worry. The Pro 8100 has lots of vertical and horizontal lens shift, so you have lots of "wiggle" room. As a guide-line, you should mount your screen so that the lower 1/3 is below your seated eye-line (to the screen).
In my case, we sit semi-reclined so our screen bottom is actually at the same height (from the floor) as our eyes. This puts our eyes aimed at about 1/3 of the way up the screen. Our measurements are: eye-height = about 37", our 106" screen is 52" high, so that puts the top at 13" from our 8.5' ceiling. Remember all screen sizes are of the viewable area. Most screens have a 1.5" to 3" black border all around them (to block any stray light). The lens of the PJ is around 2" from the bottom of the PJ (the bottom is closest to the ceiling for a ceiling mount).
Then you can mount the Pro 8100 on a ceiling mount. Depending on how high your ceilings are, you may want to have a mount which puts the PJ about 6" to 8" from the ceiling (assuming an 8' ceiling height.
Remember the PJ gets mounted upside down (you flip the image in the PJ menu). You should try to mount the PJ so that the center of the lens lines up roughly with the center of the screen (left to right). The PJ has to be level (assuming the screen is perfectly vertical). You then use the lens shift to center the image on the screen.
As I mentioned earlier, you can find out that information around page 10 of the user manual: http://www.viewsonic.com/assets/005/5446.pdf
. As for the distance of the Pro 8100 to the screen, see http://www.projectorcentral.com/View...ulator-pro.htm
for the details. That is a completely interactive calculator, and each box can be adjusted for your setup. You enter the screen size and it will tell you the range of distances from the screen to the front of the lens (= projection distance). For instance, the PJ can be mounted anywere from 10' 10" to 17' 7" from a 106" screen (plus about 1/2 the depth of the PJ).cpage
-- You don't have to apologize, those are very good pictures (with the lights off), even without a "real" screen. Those "squares" look like your room light is reflecting off of something in your room that is lit by the light(s). Screen shots are best with no room light (as you found out).