I know from you most recent post that you've already completed your Xtracycle build. However, you should have received an Avid Rollamajig with your kit. It sounds like you might be a victim of the same thing I was the victim of - not receiving all the parts necessary. I didn't get a Rollamajig with my parts kit. Apparently they just get left out sometimes. I called the folks at Xtracycle and explained that I didn't get the Rollamajig and they sent a replacement out to me right away. You'll be able to shift with a really long run of cable to make your loop but it won't shift very crisp and under load it may skip shifts or not shift at all. The Rollamajig really helps with the run of the cable line making it so that it doesn't have to be so long of a loop and thus introduce loads of extra drag from all of that extra housing. With the Rollamajig you can get an almost ninety degree cable run going into your rear derailleur. If I were you, I'd go ahead and see about having them send you a replacement, as it will make your shifts a lot more crisp and a lot more reliable. This is what you should have received:
http://www.chainreactioncycles.com/M...x?ModelID=1802
The one Xtracycle includes is actually grey-colored.