brisket & pork butt at the same time

I'm going to be smoking brisket and pork butt for work and my question is regarding times. Based off the cooking times from the Cooking section it looks like the brisket will only take about 12-13 hours while the pork butt should take about 16-18. I've cooked lots of pork butt and I've got it down but I've only done one other brisket. Would I be better off to start the butts on the bottom and add the brisket 5-6 hours in on the top? I've heard it is better to do the brisket on the bottom and let the fat drippings from the butt flavor the brisket.

I guess overall I'm just looking for suggestions as I'm providing lunch for my office and I'd hate to screw it up.

Thanks
Lexx