A mate of mine wants to position a projector behind a wall in his room. The first thought he had, to hide the hole he will have to make to let the image through, was to hang a picture over it when the projector is not in use. However now he is interested in hanging a 2 way mirror over the hole to save the effort of constantly removing and replacing a picture. The obvious question is has anybody tried this and what effect does firing through a 2 way mirror have on the image? All opinions gratefully received.