I have been asked to cook brisket for a church event in about a month, and I need some help. I have a really large gravity feed (Stump's style) smoker, and I will have - probably - 15 briskets in it at the same time. I can handle the brisket just fine space-wise, but with that kind of load at 250 - 260 degrees, am I going to encounter any significant difference in cook time? Common sense tells me yes, but how much? Is there a rule of thumb? Should I slightly elevate my holding temp, or should I just plan for a longer cook? My rig is completely insulated, and I can hold consistent temps for as long as I need to.