I see quite some people are trying your suggestion and they get different results. I wonder if the light pollution could also come from other sides of that camera/circuit board. For that reason I wonder if you can try maybe an alternative solution to fill the unit with some kind of opaque electrical resin. Someone suggested the same but of course, you cannot fill it completely as you do not want to cover the light pipe and the actual light window. But maybe there is that right angle and right amount to inject inside so that all camera/PCB is covered. As you have the unit dismantled, maybe is worth exploring another alterative. Advantage will be that the hole can be smaller, in a less sensitive spot and with the right resin to cover the entire area between camera and PCB so, a more or less guaranteed result. The “risk” I see is covering the space between the LED and the pipe light plastic.