I recently had to add a rudder reference sensor to an existing Garmin system that had none installed. The owner wanted to see the visual graphic display mainly for low speed/docking/close quarters work. It was easier to go with N2K for cable routing reasons.
Interestingly the Simrad N2K sensor appeared reversed from actual (turn to port and the graphic showed turning to starboard). Per Garmin there is no way to correct this as you would normally during setup when using a Garmin sensor with a Garmin autopilot system. This was a GHP 10.
A call to Simrad was similar.
Just posting this as a warning others not to assume N2K sensors are universally compatible. The data is on the bus but in this case was unusable.
Could you mount the RF25N "upside down"?
That's exactly what we did. Works.
:-)