Ran Map Light Wires. I twisted two 22 ga. (power and ground) wires and ran one segment from the Panel Dimmer down the left side for the installation of a pilot and passenger map light. Another wire pair was run down the right side to the pilot's position. As mentioned, the power will be from the Panel dimmer section of the power terminal mounted on the baggage compartment bulkhead. Each source on the Panel dimmer circuits will have its ground ran back to a location on the avionics power terminal and then grounded from there to the firewall. This is the suggested procedure for the best results with the dimmers (no grounding locally).
Took a second look at the dimmers for the Instruments and for the Instrument Panel. There is four terminal locations on each. Two"In" used for the aircraft 12v power and aircraft frame ground and two that run to/from the source (device being powered). I had a ground wire from the Instrument Dimmer running to a strip in the baggage compartment. I wasn't sure if this wire was needed when I initially wired the dimmers. Sources such as an LED Light Strip used to illuminate the panel will have a power and a ground wire. These wires could be wired into the dimmer's source terminals. But the Instruments' lighting uses the dimmer to control the current flowing to the instrument lights. There isn't a ground wire to run back to the dimmer. The Instrument grounds have already been wired to the avionics grounding D-sub terminal. After calling the ever so helpful Tim Haas at Approach FastStacks who made my avionics cables, it was confirmed that there is no ground from sources to the Instrument Dimmer. The ground wire to nowhere that I attached was removed.