Monitor your pit temp in the center of the grate. Shorter stem thermometers mounted on the side can read up to 50° lower than the actual temp in the center of the drum. I have both a short stem and a 10" stem thermometers on my drums.
KCBS - CBJ
Big Green Eggs, Big Drum Smokers, Big Chiefs, Weber Smokey Joe "Custom Tall Boy"
Oil Patch Horizontal
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Barbecue is not rocket surgery