I'm about to build up a frame (Motobecane Fantom CX) with cantilevers and drop bars. I plan to use my old Campy 9-speed levers. Obviously, those levers don't have any way of adjusting the cable length - so I'll have to add some way to adjust it. I know I can buy a front cable hanger with an adjusting barrel, so that takes care of the front. It's the rear that I can't figure out: this frame already has a cable stop for the rear brake, so I don't think I even have the option of installing one of those adjustable hangers on the seat bolt. I think what I need is some sort of adjusting barrel that can fit into the existing cable stop - does such a thing exist? If not, how can I make one?