There are some creative ways to use a high offset projector in low ceiling or type of enviroment.
Here is an install of HT1000 in a 7 foot ceiling HT.
How did he get a high offset projector down so low? Digital keystone correction? Nope. Serious overscan? Nope.
He tilted the projector up slightly
and the screen forward slightly
. A 5 degree tilt will give you 1 inch vertical image shift per foot of throw.
With the specs Tzung posted earlier, on the H81, it works out to about 4 degrees of tilt to turn it from a 27% to 0% offset projector. (0% means the lens lines up with the top edge of the picture.)
Some tilt is actually visually appealing IMO. 4 degrees is definitely not too much. Here is rough sketch if you still don't quite follow me:
The sketch is only for reference. (I free-handed it and then told the program to rotate it 4 degrees - I think it actually turned out fairly accurate)
This level of tilt is not objectionable. For the person in the chair the tangent line is still above their eyes so it doesn't look like the screen is falling forward.
Anyway, where there's a will there's a way. High offset is not that difficult of a problem to overcome.