I know that this is not what you had in mind, but on the chance that it might be useful . . . I sometimes need to haul an additonal bike to or from a bus station or school. I use our Burley trailer folded flat. Then I put the extra bike on top, upside down. I use toe clip straps to attach the handlebars and a bungee around the seatpost to stop the bike from sliding around. It's fast and easy. Even loosely secured, the extra bike rides pretty well.