I tried a used 2006 Dahon Jetstream XP today. Very light. Very nice. I have a question. The seat is the only thing I didn't like, but the seat doesn't have traditional rails, but more like a dual track with notches. The seatpost is a really nice, light carbon post. But it is pretty large in diameter. I don't know if it is a standard size, it wasn't marked. Any way to get a different seat on that bike without buying a new post? If not, are posts available? Or are these some kind of odd size.