If you believe that fat cap up actually bastes the meat you've never cleaned the bottom of your smoker out. 99% of the fat that melts runs over the sides and into the bottom of the pit. I have tried both ways and the fat cap down yields superior results.
the fat cap down keeps the rising heat from burning and drying out the side that dosen't have the fat.
This is dead on.
The reason I wondered about turning is that my rub never seems to get beyond the paste stage. I wondered if putting the lean side down for some amount of time would help it solidify and give a real bark and not the squishy finish I've been getting even without foil.