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purduesd
If the center of the lens is ~20" above the height of the center of the screen (29.4" is half height), the JVC being 20" high (plus 2" for a flush mount), and the ceiling 9'/108" 8'/ 96":
108- 2 - 10 (center of lens) would result in 96" - center of the lens.
Problem is if the height of half the screen is 30" and the lens shift only allows for 20" above the center height of the screen, the center of the lens is 10" under the visible top of the screen. This would result in only 2" remaining to the ceiling, and 2" is the usual height of a screen black border. So the screen would be flush against the ceiling.
Not only that, but the screen would have to start at 47.2" / 4'. That's too high.
If the difference between the two ceiling is 1'/12".
The screen would end at 80" /6.7'.
JVC height is 20" and Optoma 5".
JVC's vertical lens shift is 47" from the center of the screen, ~50".
If the JVC would be flush against the ceiling, 50 + 47 = 97" - center of the lens.
The center of the lens of the Optoma would need to be at ~80" with the possibilty of raising it by 9.4".
If using an ALR screen placing them on the vertical axis but one closer might result in unwanted visual artifacts.
17'/ 204 - 20" (JVC depth) - 4" (for cables) = 180"
180 / 104.6 = 1.72x throw ratio
Using both of them under the 9' ceiling is not possible. Even just with the JVC the throw ratio is still 1.72x. There was a recent purchase of a Cinegrey 3D (with a realistic gain of 0.8-1.0) and while there was no hotspot the user reported sparkles at 1.7x throw. The projector was a HC3800 which is bright, but I don't know if the NX5 will be artifact free at this throw ratio.
Placing the Optoma under the 8' /96" ceiling:
80" end of screen + 2.5" center of lens to top of projector= 82.5"
96 - 82.5 = 13.5" required.
Vertical lens shift can add another 9.4". 13.5 - 9.4 = 4.1"
A mount of at least 4.1" would be required, putting the Optoma at ~87" height - from floor to bottom of the projector. 87' is 7.25".
I have the 3D and it definitely hotspots at 1.5x.
Maybe just get the 5050UB/6050/NX5 and a white screen, you'll be very happy with it. Not entirely sure how it would look like with 1500 lumens during the day without curtains. It's probably fine. 1000 lumens on the JVC on the other hand, not sure.
If you want to get the ALR the projector would need to be placed underneath the 8' ceiling.