Don,
I guess my CSFP sensibilities are too offended by the possibility of the defense getting 3 outs on a routine fly ball that I would be inclined to rule "no catch" on the drop. Of course that would all depend upon how obvious the catch and drop was. If it were truly an obvious catch followed by an intentional drop, then as PU (and probably as BU too), I would be bellowing "That's a catch! Batter's out!" loudly enough to scare the runner's back to their bases.
SamC