I just wanted to be sure that anyone reading this thread would not think of adding and using an over-rotator with a spi.

You might want to consider a shock cord type of setup like we use on the Hobie 17 & 20.

They both have the arm located at the bottom of the mast.

The same setup would allow you to have a mast rotation limiter on a boomless boat also.

Go to "http://www.nahca.org/news/tiger_2003_2.pdf" page 5, for pictures of the limiter setup on a Hobie Tiger. You would simply add a loop of line and a shock cord lead forward, to add postive rotation.