Feet in the bottle cage is a neat trick, we always got Little Cudzo to just dangle his legs wide. I can well believe that many people have never seen a child trailer. In fact, in Poland where I lived till recently, they are illegal - though the law is in the process of being changed and they are available in shops. But it's still a rare sight - money and habit being the limitations rather than law. In fact, I can't think of any occasion when I've seen one in use out there.