The image you would get is already too big from the fixed 12' distance you gave. The only optional lens would shorten the throw and provide an even bigger image at that distance. You could get the lens and move the projector to a coffee table or ceiling mount it closer to the screen, but at $500 dollars for the lens, it doesn't seem like a reasonable solution to your problem. Lens or no lens, because your trying to exactly match an existing screen, projector placement has to be exactly right. A sliding tray for the projector seems like a reasonable, cost effective, minimal impact solution to the problem.
By the way, if you do build it, make it extra sturdy. I don't want you coming after me because your 75U fell on the floor halfway through it's first movie.
Let us how you end up solving this and send us a picture.
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