SeatalkNG to S1 course computer

[57BlueWolf]

I recently purchased an ES7 MFD, i70 and instrument pack (depth/speed/temp and wind). I have these installed using a SeatalkNG network with an ITC5. They are working well in a Navpod at the helm of my 30' sailboat. Power to the backbone is from a power input to the ITC5.
I want to interface these with an S1 autopilot I purchased second hand. I have the wheel drive unit installed and connected to the course computer, and also have the fluxgate compass connected to the course computer. The course computer has it's own 12 volt power. I also have what I believe is an ST60 Autopilot head installed at the helm. It's connected to the backbone with the yellow adapter plug for Seatalk1 into a 5 port connector (2 white, 1 yellow, 2 blue).
I now realize I probably didn't need that, as I could use the es7 to control the autopilot (but no matter). Of course, at the moment, it's reading NO PILOT when switched as it's not connected to the course computer.
My dilemma is how to network the course computer into the SeatalkNG backbone.
I have a white adapter cord with stripped ends, but there is no 6th wire, the Yellow Seatalk1 data cable.
I have read a million posts, including a Raymarine SeatalkNG handbook which says I can't network an S1 course computer into the backbone, but there's no date on the handbook so I don't know if that's old information?
My thought was to buy the Yellow Seatalk1 to SeatalkNG cable (A06047), cut the plug off and connect the bare wires to the course computer using only the yellow and black cables. There is no SeatalkNG input available on the S1 course computer (see attachment). Would that connect into the backbone by plugging into a 5 port connector with a white port, or do I need the 5 port connector with a yellow port?
Hoping this makes sense. Been driving me crazy for 2 weeks now!