Here's my question for the Wonks:
Wait, first the set-up...working on a friend-of-friends Bianchi with Campy 8 speed Ergo brifters, Campy cogs on a Campy rear wheel, but a broken (badly) Campy RD.
My thought was to replace that RD with a similar Campy 8-spd RD and be done, but these aren't so easy to find. I was offered an older Campy RD and started to research whether it would work with Ergo controls (not clear), which lead me to Sheldon Brown...
and he lead me to this site:
From what I can tell: the spacing between Shimano 7-spd cogs and Campy 8-spd cogs is the same (5mm).
So my theory is that a Shimano 7-spd RD will move the chain the same distance as a Campy 8-spd when asked nicely by the Campy Ergo 8-spd control.
NOW the question: will it work??
If it does then I can solve this with a cheap(er) Shimmy RD and move on