Originally Posted by
HogPilot 
Long story short, the OP has a budget DLP with limited zoom and lens shift, and this is his cheapest option for implementing CIH. Otherwise he's looking at buying a 2nd PJ, or a lens, which in this case would cost significantly more than a 2nd PJ.
"Aside from the space requirements (both vertical and horizontal) required to make this happen"
Neither are an issue, me and my girlfriend have moved and measured, and estimate 38" to 40" of horizontal movement to go from 2.35:1 to 1.78:1 CIH of 50", which works out so each end of the mount can be at 48" and mount directly to a ceiling truss... as for the vertical change (ramp up), it was much slighter then I thought it would be, and because my ceiling is high and vaulted I didn't even make note of it (My bad I was only thinking of myself)... My memory is not that great but I think it was in the 6" range and I have 24" to work with...
"the key is going to be getting everything perfectly solid/square so that the orientation of the projector with respect to the screen doesn't change as the projector moves back and forth on the rails."
This is the simple part for me, I have fabricating methods that are, simple, accurate, and inexpensive (if followed), and will provide the stopping positions within a few thousands of an inch over the 40" horizontal x 6" vertical range, and it will be more then rigid enough...
"After that, setting the stops for each A/R will be relatively easy."
In my mind duplicating the stopping points is the hard part, and I'm considering nothing less then automation by IR, if you have something in mind please share...
