Here's my update on heat. TLDR: There is a 30 degree difference between the center and the edge of the cooking grate. (Even with both probes actually inside the cooker where they belong..) The 12" thermometers I got are worthless, they read as high as 425 when the grate digital said 230.
The first spike is fixing the probes and opening the lid for a few minutes. (That is why the temps inverted - the red/center probe was actually resting inside the port, not in the center of the cooker where it belonged.)
The 2nd and 3rd are from opening the lid and/or more vents.
The probes are reading ok - they landed together at about 75 degrees when the fire finally went out. (Next time I'll switch their positions mid test to be sure, but they have been reliable so far.) Oh, and I had no stoker on it, just the probes.
Thumbs link to larger versions:
Full chart (starts about 20 mins after dropping in a half-lit half-chimney of RO on a full basket)
The overnight section (the '5 vents' label is actually 1"x1.5 vents, its cut off)
Pic of sensors - the UDS isn't oval, the grate isn't falling off, its just a cellphone pic this morning :) Oh, and the center probe isn't in a clip but it is not touching the metal anywhere, its hanging ~1/4" below the grate.
I'm going to try another seasoning burn today with both probes in clips (no more falling out) and a pizza stone resting on top of the charcoal bin. If I remember (and the mosquitoes aren't too vicious) I'll switch the sensor positions to expose any calibration issues. (And I'll move it closer to the house so I can check the vent temp periodically along with the digital probes.)
After that, I'm done burning it empty and its time to make a fatty and some ribs :)