H Bruce McCrory
I know. Late to the game....
I'm a cheapskate. So when I found 10 years of Cook's Illustrated for 25-cents each I was in heaven. They used 21-inch Weber charcoal buckets (barrels?) exclusively. I grumbled about the price those whitewalls commanded, but my new can of propane crapped out on a new replace-every-3-years gas job. It was end of season, and Ace had an 18-inch for half-price.
I did a pork shoulder. Yee-ouser! Even it maintained proper heat for 6 hours on one charge of bricks. The larger barrel has advantages. With a water tray, a train of cold charcoal following the few burners, and thermometers competing with a bag of meat and two of wood chips there is no space in an 18.
But it worked perfectly! It was the first slow roast so there was an hour of tapping the vents to set temperature. The smoke wood burned out in about an hour, per spec's. and church occupied another 3 hours. The only thing that bothered us was the greasy meat, but sirloin resolved the issue the next time.
One other thing I learned: count your briquettes.