Brisket Timing Question

Brothers, so I went ahead and purchased a 15# brisket (packer). After trimming it will be a pound less or so.
I plan to serve it Sunday afternoon (3pm) at a party we are having. The question is how long I should allow for the cook in the WSM?, Give or take 4 hrs. I've read 1-1.5 hrs per pound at 230. So going with that it could be 14-21 hrs.
I plan to start it a 6 pm on Saturday, does that seem like correct timing? I have not cooked such a colossal piece of meat, the largest before has been 8#.
I appreciate your input. I will follow up with pics.

Thanks for the advice. I do plan to seperate the point at the time I wrap the brisket (around 170ish) to make some burnt ends. I hope the timing allows me to cooler for a couple of hrs. If it takes too long the wife is going to give me the evil eye.:icon_pissed Either way I will probably not get lots of sleep Saturday night. Espresso and black sambuca will be be the bev of choice. WIRED!:icon_bugeyed

Zilla, I'd like to give that a try, just not on this one. What do you put in your injecting liquids to assure tenderness?