Bearcarver - your comment got me to thinking about the chamber temperature and how much it could vary, so today I decided to put it to the test. I used an iGrill2 with the ambient temperature probe. I did the ice water, boiling water test and hit 32 degrees and 209/210 degrees (210.532 is boiling point in my location). The water pan was empty and covered with foil and vent was open all the way. I set my temperature on the smoker to 235 degrees and put the iGrill2 ambient probe on the second shelf back middle for the tip was about a 1/4 inch from the smoker chamber thermometer tip. They both hit 235 degrees within a second of each other. Now on to the test, I took 27 measurements on the bottom, middle and top racks (9 on each rack). For each reading I would put the probe in a location and make sure the smoker temp dropped below 220 degrees. As soon as the smoker hit 235 degrees I would document the iGrill2 temp and move on. I'm not sure what to think of all these numbers but here they are.
I color coded them as follows; Green = within 5 degrees of 235, Blue = more than 5 degrees lower that 235, Yellow = 241 to 255, Orange = 256 - 275 and Red = greater than 275.