Hi Dave,
RE: rotation limiter.
You could try the system that is on the Hobie 20.
It does not connect to the boom, so it will work on a boomless boat.
The line runs from the arm, through a grommet in the tramp and cleats on the hulls.
It is easy for the crew to adjust without moving to the center of the boat.
Even the Tigers and Foxes are switching to it.

RE: postive rotator
Many people like the forward bar and cleats, but I had it on my 18sq and felt it was problematic.
I prefer the bungee cord type, like on my 17. It works with the rear facing bar.
It is automatic and it always holds the mast steady instead of allowing it to flog around in light air chop.

Are you going to the Charleston regatta?
There will be many different variations of roatators on the different boats.