I populated a second State Panel PCB with the Linear Hall Effect Sensors and  a CD4067BE multiplexer.  Only the first panel needs to have a MCP3008 8-channel A/D converter. I then connected the two panels together via the bus pins with some AWG22 solid core wire.

I designed and printed a frame to hold all six State Panels.

Notice that the second (leftmost) panel is wired to Channel 1 of the MCP3008 on the first panel  (via the bus).

One more change, I increased the size of the cutouts on the bottom of the printed panel so that the panel and the PCB now lie flush.