Not really a significant point of interest in this discussion, but I've been running Campy 10-speed on our daVinci tandem all season...with a 9-speed KMC chain (can't find a 10-speed chain long enough for the daVinci drivetrain yet...I need at least 122 links and 124 would be better. Longest 10-speed chain I've found is 116 links and I haven't wanted to splice two chains together).
I had to get a little bit creative in substituting two 9-speed cassette spacers in the middle of the cassette to cut down on a small bit of chain chatter. Everything is smooth as silk now.
But even with the stock cassette spacers, the shifting was acceptable in an emergency situation.
Food for thought...