Been following along Rick and I've finally come to a section that I can comment on, your Mimic Panel. Having dealt with small wires for the last 30+ years you pick up a trick or 2. There are 2 primary connectors available for 20-26 awg. wire. B connectors, Originally manufactured by Nortel under product number BCT-7759. usually used by alarm techs and originally used by Bell techs, and 3M Scotchlok connectors, currently used by Bell. If using B connectors, strip and twist the wires together with just 3 or 4 twists before squeezing the connector on. Both types are available with gel for outside or damp locations.
To solder small wires the best method is to "tin" each wire with solder, cut back to length as the outer insulation has now shrunk, then reheat when side by side. This results in the smallest diameter before applying heatshrink.
Finally, the terminal strips you are using can cause a problem down the road. Unless mounted with the screw heads facing up, the screws have a tendency to back off due to vibration from the engine. If they cannot be mounted with screws up, add a little loktite to each head when completed.
Great work by the way. I'm just a little jealous.