Hi
An interesting article in PBO regarding Seadog of Polruan; I am not entirely clear whether the issues with steerage was caused by the hydovane or the small rudder or both.
I have a Raymarine autopilot with a ram neatly out of sight.
There is an input for a wind vane though I just use the bearing control.
I imagine this might operate like a hydrovane; downwind the auto struggles to steer without the engine. My original pinto operated better with its valve system but long gone now.
Borrowbox allows you to read PBO
Regards
Ian