I have a B17, but haven't used it that much. My understanding is that it will take some time to break it in. Use a lot of proof ride to soften it up. Don't tighten it too much at first, you don't want to force the leather to stretch way too much.
I haven't used it because in the past, I've been unwilling to give up my bike weight to use it. But for I'll use it for my trailer pulling bike. However, I wouldn't let it get wet, hence I'm waiting for spring.
I will also consider chopping it to drop weight like this:
http://velospace.org/node/1760Sheldon Brown, nice reference. He's a freak but knows is fixes and singlespeeds.
