Actually, it is supposed to go through one. My previous H17 was stock out of the box except for replaced delam sails. Comparing the set up to the picture, this is my take:

The cleat on the side of the mast was probably added, or the mast was used in a sport (boomless) set-up. In the sport mode, you need it for cleating the downhaul. But with a boom, the downhaul goes from the sail to one shieve on the mast base, up through the double block on the sail, back through the otherside shieve on the base, up through the double block other side, down through a single block on the mast base mounted on a pin above the center halyard shieve, and then straight back though the first cleat on the boom. The rotation limit line is tied to the top of the second camcleat from the mast, runs though the rotation arm, then back through the same camcleat it is tied to. One camleat for the downhaul and one for the limiter.

At least this is how I always have set both of my H17 up.

Hey Nigel, aren't you the one that had that fancy rotatoin setup on the Yahoo H17 site?? Did it not work?

Mike