<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">generally letting poultry drip onto anything other than more poultry is bad. </div></BLOCKQUOTE>
Sorry, but this is not true. Oft-repeated, but not based in food science. First, as long as both are cooked to safe temps both are safe. Second (in the scenario you note), the internal temp of the pork below is immaterial (it is material for the pork itself, but not for the chicken juices dripping from above). The salient issues are the temp of the surface of the chicken at the point where the juices exude, the air temp in the space where the juices drip, and the surface temp of the pork below (where the juices will land). If any of these temps are >160? (and one can presume they are) the juices are pasteurized in seconds.
That said, I almost never combine meats in a cook. The rubs are different (I don't want the rub flavors from above dripping onto the meat below), the quantity of smoke I want is different (for chicken I use less than 20% of the quantity I use for ribs, if I use it at all), sometimes the wood is different.