Interesting post Kitch. Built in thermos aren't good at all... in my opinion!
We dont trust them at all. As a matter of fact, the PQ E 20 lid thermo was WAY off on yesterday's cook (actually way more off than it has been on previous cooks).
We have always monitored our temps at grate level, using our cheap-ass Mavericks through the eyelets on the PQ E 20.
We did two racks of spares today on the PQ E 20. We cooked both racks on the top grate doing a 2 stacker cook. Basically, the lower stacker and grate were lonely. Nothing on them at all, and just trying to fine-tune the cooker.
Lisa loaded the bottom basket w/ about 1/3 unlit Blue Bag K and dumped a fully lit chimney of Blue Bag K on top of it. Water pan was actually filled with about 2 quarts of water (which evaporated after the first 2 hrs....and no more added).
On two stackers, with us cooking only 2 racks of ribs on the top stacker, we were in the 215- 250 range at top grate level..consistently for 6+ hours (nothing on the bottom grate). We actually had to shut down the bottom vents to drop the cooker back into the prime temp range.
We've had no issues with consistent temps..well at least after our first 2 trials.