Firstly, many thanks to everyone who answered my question on rig tuning. I now have a much clearer idea of what's going on.
I am looking to acquire a self steering device for my J30, Hull 126 "Shanti". I emailed Scanmar and asked if a Navik system would be suitable for the J30. The advice I was given was that I would be pushing the limits of a Navik and they recommended a Monitor. I was told that Monitor wind vanes had been fitted to six J30s but some years ago. I was a little concerned about the weight out aft.
I would welcome any advice on the above especially if you have fitted a Monitor wind vane or think that another make/model would be more suitable.

Mark R. Leach