Bud you are way over engineering this..
Think K.I.S.S = Keep, It , Simple, Stupid,....
rubber door trim...
Run something like this around the back side of the Large housing to seal the P1 inside.
Theres all kinds from round to blade edge, from 1/4 to 1" thick..
Rubber door trim Noone will ever see it and all you need it for is to keep the inside of the outter glass lense clean on the inside.
Its never going to melt.....
I am real curious to know what those fog shells would look like with some chrome paint on the inside walls and maybe even paint the outside of the P1's chrome..
would probly enhance the total lumen output greatly .
Yeah, I'm good at over-complicating things. I managed to over-complicate my Fusion projectors pretty much to death...lol. It would be simple to keep the mount like it is in that pic, just plain-jane and KISS. And I may go that route. That's why I was talking about Home Depot and finding something to finish it. There are a variety of ways to seal up the back, I just need to go shopping.
Oh, and why did you have to mention painting the inside of the housing chrome?? Geez. Now I just MAY try that....