Those large flats are rare, generally, they are in the 6 to 8 pound range. I typically try to get 8 pounders.
I also cook fat side down the whole time, as I having tuning plates, which have a lot of radiated heat. I also tend to cook on the bottom grate..........maybe the second grate would be better to avoid drying out??
I check the temp in the thickest part of the brisket (for a flat). If it's a packer, which I rarely get, I still check the temp in the thickest part of the flat, never in the point.
Thanks for all of the advice,