Well,I'm no brisket expert-but the guys are right on.
I think the comp cooks will tell you to pick the size you like,get it tender,and write that time down.
You can hold a tender packer for several hours at a comp for timing.
You can't fix underdone.
After a few you will wind up with a "normal" time.
An example would be that we know a choice 15-16 lb packer,trimmed out ,takes about 65 mins/lb.,cooked slow,"normally".
You can always speed it up.
There are a few "hot" cooks that pull 1/2 hr before turnin,but many are done at least 2-3 hrs early.
Just my $0.02