Dave-
We fix our briskets that way, but we do it with the fat cap up, after 15 hours, that pan is about 1/4-1/2'' full of juice, it kind of self-bastes it I guess, very tender & flavorful, we sprinkle cayenne in the with the juice that gets rendered and dump it over the meat before eating it. The most interested part is that the fat cap is all cracked and damn near dry after cooking, I attribute it to all the fat and juice being rendered after 15-18 hours. It's definitely worth a shot to try...