One of the rigging manuals that I've come across has the following:

"The Nacra F18 is equipped with two lines that hold mast rotation on
downwind legs when spinnaker is raised."

My boom has a jam cleat on either side, and I found one picture that shows lines running forward toward the mast from these cleats, so I assume they are part of this rotation aid. I haven't found anything yet that suggest where the lines attach to the mast. Anyone know? A picture would be even better...

Thanks,
-Robert