Kees, My concern was if the compass which is dampened would be
responsive enough for stable overlay, so I think we were thinking the
same. If I make the purchase, I agree that it is worth while to give
the existing system a chance to work properly.

Last season I purchased a USB NMEA multiplexor(Brookhouse) and have
hardwired my autopilot output to it. My compass heading comes through
the autopilot and is converted in the autopilot from sine/cosine data
to NMEA data. If it overpowers other data, I will at least have
understanding why and maybe can reroute to a serial port.

My goal is to find a system I can install with minimal problems since I
will be purchasing it in the states and installing myself on the boat
in Mexico where there will be no easy access to customer support.

Thanks again for your insights.

Larry