Ooops...... the curse of posting when half asleep has stuck again! I saw the thread title in the scrolling new post summary page and did not notice it was in the "cold smoke" section.
On that note, the pellet tray works fine as a cold smoker in a
WSM. I've done it several times and have even used a small electric hot plate as the heat source in mine. I did that as a test to see if I could do the whole smoke of a batch of snack stick and slowly have a stepped transition from cold smoke to final smoke/heat. It did fine. I've even thought about using a brinkmann element and a PID controller for just this purpose with sausage and snack sticks.
As long as you have adequate air flow to the pellets, that tray (and I would presume the tube as well) are great. So yes, cold smoking with no charcoal and no heat would work perfectly in a
WSM.
One thing I have found is that no matter how hard you try to keep them dry, the pellets seem to absorb free moisture from the air in storage. I have had this issue with different brands, so it appears to just be the nature of pellets. When I use pellets I will dry them out a little before use. 1 to 2 minutes in the microwave before putting them in the tray works for me. It is surprising the amount of moisture you will see on the sides of the container from "dry" pellets after a quick trip in the microwave. They start great with a propane torch after that.
I've used mine for both dust and pellets, but I like the pellets better. Oddly enough I don't recall having the moisture issue with the sawdust, just the pellets. I guess it has something to do with the way they are pressed and made?
As to the altitude, I'm about about 800 fee above sea level, but I'm in Georgia so the humidity can be brutal at times.