I got it to work OK with a Chorus rear derailleur with the A/B switch (on the B position), the correct insert and a Dura Ace 6-speed freewheel. This on a 1988 Cannondale Criterium that a previous owner had made all Campy. But the shifting wasn't even close to as crisp as the Shimano 7- and 8-speed setups of the same era. Plus, I simply could not get it to work well with 7-speeds and I tried lots of different inserts and derailleur settings. If you watch the derailleur in action, it actually overshifts then springs back, just as a human might have shifted using friction!