Each board is being wired as a stand alone unit, each with its own connection cable back to the control panel.
Board 1, the one with the grainstore and station buffer stops, has four sections. Board 2 has the most sections with 7.
Them wot knows electrics will note that the switches are wired using a common return (red wire) with the black being switched. That means, on the power supply board to control panel cables I'll need up-to 8 wires (board 2 will have 1 red and 7 black).
My first thought was to use bog standard d-sub sockets and ready made vga cables. The digging I did revealed that although the d-sub it's and sockets could take an appropriate ampage, the ready made cables really weren't up to it. There appeared to be a good chance of the single red return wire getting cooked in DCC mode.
I did think of wiring 2 pins as the common return but then found that many of the pre-made vga cables already group pins using 3 each for RGB.
Looking around for other options I found these GX16-9 plugs and sockets. Robust, professional units used for aeronautical and microphone applications.
It would mean making my own cables using 8-core multi-core cable (7x1mm2 and 1x2mm2) with the 1x2mm2 used for the common return.
The max interconnect run between boards and control panel is 4m by the way...
Still some thinking to do on this I think.