The Heron was originally marketted as the YW Cartopper and you could buy proprietory sliding roof racks that did just that. Much more satisfying to make your own though. Many of my old cars had dented roofs when loading dinghies didn't quite work.
The heron, however, was the first boat I was taken sailing on. My father built one, I’d have been under 3. My earliest real memories are of him building the successor, a Mirror, naturally.