I typically do a butt over a brisket, I like to run a full cooker if I can. I think it makes a difference. However, I also do not believe in mopping, there is no reason to believe it, or basting for that matter, does anything but glaze the meat.
I like the idea of foiling the flat per Wampus's suggestion, flats are notorious for drying out on a cook. And it is hard to get it heated again if it does dry out.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."