I use the N-Gear Jumpstop (with 26-38-48 chainrings). All you have to do is bend the top a bit so the derailleur clears the top. I'll post a picture tonight. I'm too concerned about gouging the cf not to use one even though as TG mentioned the chain would probably end up on the BB spindle.
Last edited by rmac; 06-17-09 at 08:40 AM.