It's clear you've been around the block with BBQ having knowledge of the Wilson 640 XL.
Thanks, Luvtosmoke,
I forgot to ask how you came by the Wilson 640XL. I would love to find one. Many moons ago, my neighbor in NY had one and it is the only one I have ever seen. He was a physicist and, I believe, he worked at Grumman Aircraft in Bethpage. He was a little sketchy as to how he acquired the Wilson, but I think it was designed by his boss.
When you looked into the grates, you could see that there was something very unusual in the configuration of the smoke distribution. I believe he referred to the effect as an "asymmetric vortices" design. I remember that it had two control handles under the oven that he adjusted at the start of the cook. He remained vague about the design otherwise and would not remove the grates for a better look.
Other than that, I can say the smoke quality and consistency was spot on, and the temp. was clearly stable; he hardly ever had to adjust any control during the cook--- just added fuel.
I would appreciate anything more you can tell me.