I've had the stock Cyclone GT RD on my Nishiki, running with a Campy 8sp cassette. I was curious and thought I'd switch out the Cyclone for a shiny and much-touted Superbe Pro RD I had kicking around, but set-up, I couldn't shift the chain onto the 3 lowest cogs.

The Superbe is listed with a chain wrap of 26T, which should be fine with my cassette. Could it be that it just doesn't have the lateral range to get through all 8 cogs? It's not a limit screw issue, just to cross that off the list.