Bob,
Since you haven't decided on a specific projector model and are currently running wiring, you should consider a couple must have features. The wide angle lens (1.5 to 2.0 times zoom) will accound from the mounting distance issue and the lense shift feature will account for a vertical or horizontal offset of the lens to the screen. The above mentioned Panny AE900U and Sanyo Z4 have these features but many DLP projectors do not.