Hi Cary,
In the factory configuration, the "V" shaped arm facing aft and cleated to the boom, is a rotatation limiter. When we attach other lines to it to force rotation, it also functions as an over-rotator.
The big bow arm facing forward is used as only as an over-rotator. I don't think any boats come with these from the factory.
On the 18sq, many of us would flip the "V" around forward and only use it as an over-rotator. Some would replace the "V" arm forward with the "bow" arm for better over-rotation.
The elastic design I use was copied from a Hobie 20.
It works very well on the Hobie 20, which has a larger, heavier and tighter mast than a 5.5.
I could flip the "V" bar forward and use a postive lock system like I have on the 18sq. but it is not worth it.
I'll show you at Lake Murray.