You're still going to need 1 1/2 to 1 3/4 hours per pound. Be careful if you're buying a "trimmed brisket flat" because most of the time they trim off damn near all of the fat, leaving a very tough, lean chunk of beef. That makes for a tough, dry chunk of cooked beef.
Don't ask how I know this
CBJ # 22569
KCBS BoD Judges' Advocate
Member of the 100 Contest Club
Possibly the only judge ever to get an award from a bunch of cooks
UDS 075 UCB WSM and a bunch of other stuff.
The above post is only my opinion - mine & mine alone.