I have a 9speed 12-23 cassette and downtube Suntour Power friction
shifters on a road bike, it works well once you get the hang of the
small amount of movement that is required.

Given the precision required I can't imagine shifting while bouncing
around in rapidly changing off-road conditions, but it is conceivably
possible for somebody with more talent than myself (not hard to imagine).

In the heat of competition I'm pretty sure the elevator would be
regularly missing floors.


Marcus