Campagnolo 9- and 10-speed mixology

[smontanaro]

I'm trying to get prepared for my next project, building up a rinko bike using an 8-out-of-10-on-5 setup. Weird, yes, obsolete, mosdef. My plan is to use a 8 cogs from a 10sp Shimano cassette with Campagnolo 10sp spacers on a Grand Bois cassette hub. While not entirely straightforward, I think I can pull that part off, as the bits are easy to find and not terribly expensive if the experiment fails.

More interesting for me would be figuring out compatibility between 9-speed and 10-speed parts. If I understand correctly from perusing the web (Branford Bike, most especially), the post-2000 9-speed rear derailleur should be compatible pull-ratio-wise with the 10-speed derailleur. Either would work for this exercise, right?

The gearing I have in mind would probably require at least a mid-length cage, but those seem to be uncommon in 9/10-speed. (I see a medio – 72.5mm – cage in the 2008 Veloce catalog.)

Moving on to shifting... Are downtube 10-speed shift levers available (downtube shifters make rinko-izing a bit easier)? I see bar end shifters for time trial, which are apparently relatively easy to convert to downtube use, but were actual 10-speed indexed downtube shifters available? If not, I could use brifters or learn to friction shift the narrower spacing via the downtube.