Probably NOT what you're looking for here, but in the future if you think you're going to be pressed for time for whatever reason, you can always turn out a high heat brisket and do a full 14-15lb packer in UNDER 4 HOURS. Yes, I said it, and i've done it myself.
The secret is assume two things:
1. You're not interested in bark development. Brisky cooked at high heat doesn't not develop any type of bark that is traditionally associated with brisket. If this is not a primary concern for you, high heat is a good way to go.
2. You have 4 hours of time, start to finish, from loading the smoker to removing it and letting it rest. Again, i'm not kidding, it can be done.
Crank your smoker to 350 degrees, toss several chunks of wood in for flavor. Cook uncovered and unwrapped for 2.5-2.7 hours. Pull and foil. Return to smoker and run at 350-375 for next hour. When probe enters either vertically or horizontally into any part of the flat like a hot knife entering butter, it's done (I usually pull just shy of this point as the brisket will continue to cook once wrapped and resting in the cooler). Pull it, wrap in towels and put in a cooler and rest until ready to serve.
What you get is a melt in your mouth, tender, moist and juicy brisket with a great smoke ring and very little bark. Probably not for everyone, but like I said, if you know your time's short, you can still pull one off. I have before and I got the idea from reading about guys who've got over 100 HH briskets under their belts.
Again, just for your consideration.