I think you don't need to bullet proof the xy IR beam matrix.
Can't rely on that, wherever there are people there are mistakes.
You can place the IR LEDs and Sensor arrays 2 each about 3 feet away from the target, and each IR array intersecting at 90deg. exactly at the bull's eye.
what about weather conditions, sun rain dust, etc...
and expect he is also going to publish the whole project
Not without my partners approval which looks doubtful.