I thought about that, too. Held off, though, after I dumped the coals in the charcoal baskets. The funky chemical smells from the kettle told me this needed to be a dry run.
I put 20 in each basket, arranged the baskets on either side of the grill. Put the probe in the middle of the indirect zone. Top vent wide open, bottom vent just about closed.
It heated up to 380 quickly, held there for the better part of the hour, then slowly started to drop. It was still about 350 at one hour from dump. It's been a little over 90 minutes and hanging at 310.
Oh yeah and as usual the lid thermometer is about 50 degrees off.