Campy 12-30T, 10s Record short, compact.... help?

[chismog]

Epilogue:

Medium cage did the trick. With a chainstay <41cm I now assume I will need the medium to use the 12-30. It works super smooth with room on left on the B screw. I think this is the ideal setup for this cassette + chainstay.

I tried a RoadLink too, with the short cage. With the tab resting against the hanger stop per instructions, the RoadLink was rotated forward, slightly. This in turn moved the derailleur towards the front of the bike, slightly... but enough where I could no longer easily get the cassette past the derailleur pulleys. The short wasn't going to wrap the chain I need anyway, so I gave up on the RoadLink approach. I can see where it would work, but it wasn't going to work on this bike. More specific than I thought.

Also, measured the chainstays of the bike I have with short cage, 12-30, 50/34... they're 41.5, which is the same as the original bike I also had this setup working with. Seems to confirm it's the variance in the chainstay length that allows this combo to work/not.

Thanks again.