Lou- Beautiful little airplane. Cavallino is a nice touch, too. They won a lot of aerobatics competitions, too, before the slow performing aircraft took over.
I think S1S were the later factory build ones, but I could be wrong. The S2S was a single seat S2, I believe.
I haven't flown the Pitts yet. The Eagle is enough for me. I didn't go in on the Pitts (wife wouldn't have liked it!) Someday I'll fly it.