I see many of the Cape Horn
installation photos show steering lines
attached directly to the steering quadrent, which allows the vane to backup the regular steering in case of a steering cable faillure, etc.. This is also a benefit of the below-decks auto-pilot
with tiller arm (although the below-decks AP w/ tiller arm still works if the bolt connecting the steering quadrent to the rudder post fails - rare, but happens). Of course most wind vanes attach their steering lines
to the steering wheel instead, so the Cape Horn
method seems like a better approach if you're concerned about redundancy (I'd need a few weeks of therapy before drilling that big hole anywhere near the waterline though). If the vane hardware itself fails (and therefore the small tiller pilot isn't useful either), for me it'd be nice to have the below decks auto-pilot
available as a fully redundant AP system. I'm waiting a while to install a wind vane (since I'm only crusing locally for now), so its nice to use a capable AP in the mean time. I notice the Hydrovane has an option for an actual backup rudder, which is appealing in the spirit of having as much redundancy as possible for long distance crusing. Even with a below-decks AP, I'd still add a tiller pilot to work with a vane for low energy consumption (and additional redundancy).