I think that too often pano photographers look for the wide open expanse, rather than what is nearer them. I believe that since I have begun looking for images containing an important object very close, 10 feet or so, to the lens my images are stronger. On a recent trip with the 717 every strong image I returned with contained such an object, and the middle grounds and backgrounds seemed to become more important and tied together in a stronger manner.
I generally use a 12" on the 717. About one in twenty images are made with a 15" or 19". The wider lens just pleases me more.