I can't remember who I got the idea for smoking a butt over the brisket from. Chris maybe? Kevin? Bill Arnold maybe? I don't remember... nevertheless, I didn't make it up myself. I HAVE taken the method to heart though, and do it on a regular basis.
Whether it's cut in half or left whole, the brisket still needs to get up to at least 188 in the flat, and preferably a little higher in the point. I've never cut one in half to cook, so I don't know how that affects the cooking time. Just out of curiosity, why are you going to cut it in half?
The brisket pieces may get done before the butt - if they do, and MINE usually do by about an hour, just take them out and let them rest while the butt finishes. If you don't want to wrap them in foil and toss into an ice chest after they come off the cooker to rest, just place them naked into an immaculately CLEAN ice chest that you've rinsed with very hot water, and they'll still stay hot for several hours. That resting time really makes a difference in tenderness, in my experience. When I put a B&B on the cooker around 8:30 or 9:00 pm, we're eating at noon the next day, USUALLY with no addition of fuel. I've gotten as much as 16 hours of cooking time on one load of charcoal using the "Minion method".
I'm a rookie compared to so many of the big-time pitmasters on here, but I learn quickly from them, and when something works I like to pass it along.
Anyway, that's my experience, for what it's worth. Your mileage may vary, of course... /infopop/emoticons/icon_biggrin.gif
Keri C
Smokin on Tulsa Time