We have been using 10X10X9 square baskets for a year and doing fine. Just last week my BBQ partner made round ones that we were about 16 inches across. I was afraid they'd be too big, but man am I a believer now. I was able to hold temps for a very long time and go hot N fast like I've never done.
When I die, my goal is to have a visible smoke ring when the coroner cuts me open for the autopsy.