The cam question is coverd in detail in the FAQ section...
All of the 20s have a standard rotation limiter. That is a rotator arm at the mast base with a line system running to each hull.
The rotator (positive rotation control)? There is a standard system we have on the 20s now. There is a comlete assembly manual (pdf) in the support area (Support link at the top of this page). Here is a direct link: http://www.hobiecat.com/support/pdfs/H20Manual.pdf
This explains both rotation systems.