I am working to wire a dynamo powered rear light that will be attached to my Tubus rack. The rack is attached to my Thorn Raven. I can come out of the headlight go around the stem and follow the other cable housings to the back of the bike. Now however, though those neat looking braze-ons that organize the brake and shift cables are in the way for running the tail light wire. When I get back to the rack I don't want to follow one of the tubes nor do I want to leave the wire unsupported. I had hoped to run it in a length of unlined cable housing but the housing is too narrow a diameter. Any ideas? Does anyone make a larger diameter cable housing? Thanks