Thanks for the tips!
I changed horses, after seeing your tip, I ordered a Kuhuna, then I was studying in more detail how this would all work on my 850. I stumbled on another brand cold smoker (Bella's "Smokin-It") and, well, it smoked the Kuhuna. It uses only pellets, lights in 20sec, runs up to 8 hrs!, and is much cooler, like 80F Cost is a tad lower, it's all stainless steel, and it mounts better onto the 850, so the Kuhuna got cancelled.
Here's a great video comparison;
I'll be putting it in on the left side, but down under the shelf. I'll cut a square hole in the shelf for the smoker, with it's lid flush with the shelf top surface.
Here's the link to the unit;
cold smoke generator
www.smokin-it.com
I loved the idea of the Sear Station mod on the left side, but I'm settling for the "just adequate" Traeger 500F to sear so the smoker can go here.