That is a good idea. I am very interested on this because maybe we should replace the 4K7 resistor in the MacArthur HAT by a variable resistor.
Seatalk1 devices wait for the idle state (+12V for at least 10/4800 seconds) of the bus to send data, if you do not use the correct resistor for your bus, you may have been forcing a "busy" state (near to 0V) unintentionally. You will notice that because your device (any Raymarine MFD) will stop sending data to the bus when using the wrong resistor.
Seatalk1 devices wait for the idle state (+12V for at least 10/4800 seconds) of the bus to send data, if you do not use the correct resistor for your bus, you may have been forcing a "busy" state (near to 0V) unintentionally. You will notice that because your device (any Raymarine MFD) will stop sending data to the bus when using the wrong resistor.