What do you think divan? I think this will work better if the device is not too short. If the beam angle is very shallow, then the dot will be smeared out and become weak. As just a rough estimation, a 3mm round dot will become a 3x50mm oval if the beam starts 100mm off the ground and travel 1m. A 45 degree angle will probably give the best result, but it don't have to be near that steep either.