Sorry for the delay but now time to finish this.
With the hole drilled for the arm bolt and the drive mounted the next step is the rudder position sensor (Simrad RF25 NMEA 2000 sensor). I scoured the net for reference photos and saw a few where the position sensor arm used the steering quadrant as an attachment point. After an hour study in the aft lazarette I could see no way to make that work. I decided to use the tiller arm as the attachment point and build a custom base to support the sensor body. It sits right next to the rudder shaft parallel to the beam.
I used some plywood scraps and a 4″ square piece of box aluminum (ebay) to make the platform and riser. I tucked it in as tight as possible to the rudder shaft so the Sabre quadrant/steering covers would not interfere. I also made it easily removable from the base in case the steering stuffing box needs servicing. The base is epoxied to the hull with a few layers of fiberglass cloth.
I attached the other end of the sensor to the tiller arm using the threaded rod attached to a small stainless L bracket, screwed (drilled tapped first) into the tiller arm. I don’t have any good pictures of this.