David, many thanks for your reply.
I love the HWV made by you for Waverbird. It is easy to understand, to make at home and sea proved.
I made my homework and sketched the HWV into a base drawing of the astern of my boat. The astern part is huge, almost like in the XVI century caravels. So , to have the vane somewhere between the deck and main boom, the at least 500mm extension is required. Easy, but where the carrier axle should be located? At about 500mm, as in the original project, or 500mm higher, or somewhere in between? In the first case the Vane assembly would swing asides and the control lines too. Raising the axle will increase the arm, torque and forces generated which I would prefer to avoid. Compromise by putting the axle somewhere in between would reduce the unwanted effects, but where is the safe compromise?
At what maximum angle does the self-steering gear swing sideways? 25deg as limited with a green line in the pic.15?
Having all this in mind, splitting the vane and carrier assembles is tempting, despite an additional mounting is required. But all dimensions and geometry would remain as originally made by you.
The vertical tiller is located in the central cockpit and steering lines from connected rudders are lead there.
I need to get to the cockpit two kind of HWV lines. The tiller control cables are routed along the sides of the boat, and the course control ones I would rout across the deck.
I think I will make the hatch in the rear cabin wall anyway- there is too much gear to be served or repaired not to have a secure access.
P.S. I am subject of another temptation - replacing the rudder gudgeons (hinges) with lacing.
Wishing all the best to you
Kris