One fun thing - I ran and will set aside a 12-line expansion block, running firewall to instrument panel. I bought 5 meters of 12 conductor shielded cable, with tinned copper conductors. The individual wires have a conductors with a cross section of 0.75 mm, just slightly bigger than 19 AWG. It's not a perfect choice since individual wires are shielded in PVC rather than tefzel. Bob Nuckolls notes that PVC was used in a generation of Cessnas and he sees it as appropriate for use on the cold side of a firewall. That works for me. One end of the cable was wired on the bench, the other standing at the side of the airplane. I made it once with the full length of the cable, figuring I would have a big service loop. I thought better of it, and cutting to length saved 11 oz. Tested for continuity and cross feed and no problems. The rear end is at the lower left of the cabin side of the firewall. The forward end is on the passenger side of the panel, secured to the panel with rivet nuts (great when working the aluminum!). I built and installed the one end, then figured out I needed to set the path of the cable to travel alongside my 4 AWG runs. Solution? Chop it off and do it again. The shorter cable did save 11 oz., and I understand it takes that kind of weight discipline to make this project a success.