I just did a 6.5 lbs flat from Sam's cause they had no packers available as well. I smoked the flat with Hickory/Pecan and rubbed heavily in Montreal with cayenne. Smoked at 200 for 2 hrs(for increased smoke absorption) then ramped up to 325. I've been doing more and more hot and fast briskets. Once the brisket hit 150 foiled till 185. Once at 185 unfoiled to crisp/darken bark. Brisket was officially done at 206 (probe tender everywhere). I saved my foil drippings and used it as a drizzle. (Make sure its not bitter thought.) This time my drippings tasted great! Once pulled from the smoker, I wrapped in butcher paper and wrapped in towels and placed it in a cooler. I rested for 2 hrs then sliced. Even after 2 hrs it was to hot to hold.
If your plans are to have it ready by 130, I would have it resting by 1130.
Theres nothing worse than being stuck in the plataue phase of the cook and being on a time constraint. My brisket got stuck at 179-183 for almost 2 hrs....then once it broke, it hit 207 in 40 min.