well really the rear of the projector housing is acting as a heat shield for you for the most part in that case, it's containing much of the bulb heat. the rear part of the projector doesn't fit inside the headlight as you can see and I could not cut a big hole like that, so I had to use heat shielding to take the place of the rear projector housing.you won't really need any heat shielding with the rear housing in place but it will get pretty hot too.
not sure how your planning to waterproof this if you cut the back out, even the bulb fitting to the projector is not a waterproof connection & is meant to be contained inside the sealed headlight capsule, not outside like that. the projector rear metal housing will get pretty hot so whatever you use to seal it up has to be able to take the heat.
by cutting the back open like you did you just turned this into a much bigger job, the good thing is you can get true double illumination if you aim it right and get it back to waterproof. if you don't care too much how the back of the headlight looks then you should be able to mount and aim the projectors, then silicone the crap out of the whole rear of the light and projector and bulb and everything, silicone should be able to stand up to the heat of the bulb in that housing I think. it may look a little like a butchered up mess from behind when your done but it should work good if that's what you have in mind. to me once the back of the headlight is cut, might as well go all the way like the original dual projectors I built for my FX and build a housing to contain what you've done there.
