Surely the lens will distort the image? In theory you could compensate for that on the printout ...
i did include the idea in my first post but scrubbed it because of this.... iv just had a quick google though and can only find refrence to the "key stone error" which can be dealt with by mouting the projector so it its projection is square (or use the onboard correcter that you find on most machines)
needs more google time :)