while visiting a friend's shop the other day, I noticed that he still had a couple of his now adult son's BMX bicycles that are at least 15 years old... rather than a folding bike, what about a seat post extension, and handle bar gooseneck extension to allow one of these short bikes to be ridden in a traditional upright fashion.... with the handlebars stored parallel to the frame, it would not take up much room.. most are very high quality and lightweight.. most of the kids in the BMX competition go through several size upgrades during their careers...