I do not know what this topic is about but the illustration seems to show a Brompton luggage bracket with a extension added. The topic title suggests a way of fitting Brompton bags to a Tern or a Dahon?? Why not get a Steve Parry bag carrier or buy a modern Dahon with the head tube luggage bracket welded on!?........Its very easy to adapt the Brompton luggage thingy to to fit the Dahon head tube bracket........