Glad to see some life left on this thread. Sad that the Birdy has become a bit of an orphan in the states. Have been running a medium cage SRAM X-9 derailleur on my 2006ish Silver with a 34t XTR cassete and trigger shifter with no problems. Very precise.

Getting ready to start the upgrades on the Gobike, and will toss up some pics comparing it to the Birdy when it gets going.