I had a Hydrovane on my Santorin. When it worked it worked beautifully.
I took it off and sold it. Occasionally it would not quite hold the boat and I had to release he locking on the wheel to put it back on course. When we encountered Sargasso weed it gathered on a the vertical rudder and prevented it working - the weed slid off the keel and main rudder because they are not vertical enough n the water. There is significant wear on the gel coat on the stern from the pressure of the Hydrovane mounting.
My decision was to carry a second motor for the rotary drive. My Santorin generates enough electricity with he shaft alternator to steer the boat plus the sun extra fuel solar panels. I do check the stiffness of the steering cables and an play in the steering rack following Aloha’s and experience.
The Santorin may well benefit from engineering systems from the SM on a boat which is smaller and not so heavy - almost over- engineered, but no complaints there.
Steve’s experience on Aloha is the only occasion I have heard of about a steering breakdown on an Amel.
I trust my 27 year old boat more than many new boats out there. When I bought ‘Ocean Hobo’ an old French gentleman passed by on the pontoon and said ‘M’sieu, you ‘ave bought the Rolls Royce of yachts!’
How right he has proven to be.
Good luck in your search.
Ian ‘Ocean Hobo’ SN 96