on full packers i pull it out at 185f and just let it rest. this is for 14 pound average weight. resting time is about 30 mins and then into holder set at 145f. the weight of the meat will carry cook to about 190-192f internal. the biggest problem i see with flats other than fat content is the weight vs thickness thing you have already observed. while your carry over temp will not be as high the biggest bear you are up against is the thin end been way over done and the fat end not really there on temp. that's why i suggested you find what appears to be the average thickness and stick the remote there. only other thing i can think of, and it sure would be interesting to do, is use 3 remotes placing them in the thin, middle thickness and fattest thickness and just kicking back with a beer and writing readings down. would be an interesting insight but you run the risk of your wife thinking you aqre nuts just like mine does. ah the price one pays to the brisket gods
jack