Mine have always turned out good FSU but will experiment FSD. I can see how cap down might be real good on UDS with all that loving goodness dripping down onto the coals then steaming back up to the meat.
I like the thought of the fat protecting the meat too. My last one on the Weber got a little more cooked on the coal side using Minion.
2004 Weber Performer GREEN
Orange Super-Duper Fast
Taylor Made 9deg. R7TP w/S-Fujikura 6
Rescued 2002 Weber Genesis Silver B Gasser
SJG Tamale Pot Mini Smoker (SJG was a rescue)
18" Gold (rescue) SJS (rescue)
and a Pyro FIL