4.2 MAST. The extrusion length and position of the mast head, mast
hound, jib halyard strap eye, spreader and mast base are not to be altered
in any manner. The gooseneck and diamond wire tangs may not be moved from
the factory supplied position. Rotator arm maybe relocated using the new casting, control system is open.

http://www.nacraclass.com/N20.htm

Sometimes you need to check things out for yourself. I believe this was covered in a Class newsletter.

Ted