We’ve just bought a Nauticat 39, which doesn’t have hydraulic steering. We used a Monitor wind vane on our steel 42’ ketch (18 ton) exclusively to cross the Atlantic, Pacific to Tahiti, south to the Austral Islands, to Chile, and later north to Florida. We rarely steered at sea, whether we were in light winds or in the odd fairly violent weather. The Monitor just worked.
We are fitting a Monitor with a swing gate so we can use the stern steps. It won’t work with hydraulic but if you can revert to a Whitlock type system it just works. We’re going to the lay up lunch. Ian S