Gotta disagree with the BBQ folklore, as I don't know what chemistry you're talking about. Sure the fat will melt, but it is not going to get into the meat. It's a nice idea, that "bathing the meat in fat will impart flavor". Unfortunately, it's science fiction. Sure, if you leave the fat, most people go fat cap up. Probably best to trim it to 1/8th inch thick at most. You are right about the time though... you need to get the temp up to where the collagen (main part of the connective tissue in the meat) breaks down. That's what makes this cut tender.