Reading your reply and looking back at the video again, yeah, your setup probably makes a huge difference. That pan probably acts as both a heat sink and a diffuser plate bringing the hot air up the outer edges of the RK. Basically, it's like a huge WSM.
On mine, I'm running completely stock. Snakes on the charcoal grate with the cooking grate right on top of that. A single snake will hold temp on the side of the grill that it's running on, but temps on the other side are much, much lower.
One of my clients is a sheet metal shop, I might just have to talk to them and see if they can duplicate your setup!!
We did have 2 temp probes running there was a difference of about 10-20f at some points during the cook(haven't tested the Mavericks for accuracy for a while) The large pan we use is quite thick and seems to work well as a heat sink and also to distribute the heat evenly through the ranch. In saying that I'm sure the side of the ranch where the fire is would be slightly hotter than the opposing side but that's to be expected with any snake setup in any kettle.
Here's a pic of a recent cook with 20kg/44lbs of pork shoulder
I find the centre seems to run a little cooler than the sides of the kettle but haven't had the differences in temps like you mentioned. Most times we run with 1 bottom vent open and the top vent open once the ranch is up to temp and we are past the C.M.D. (Cold Meat Factor)