Excellent write up.
Did this upgrade about 2 years ago because while towing the pop-up camper with it's fridge in 12v mode, it's battery getting some charge, both a/c units running and sometimes having sections of road that require daytime headlights, I was seeing voltage down in the 11-12 range. Not good. I went with some large gauge stuff, including the run from the starter solenoid to the junction on the firewall. Made a big difference.
I'd been doing this mod on all of our cars for years, after working on German cars that suffered from small cable syndrome right from the factory. Back in the mid-90's the Volkswagens in the Los Angeles area were dying on the freeway, in the middle of the day.....with dead batteries. I was a tech at the local dealer at the time, but had come from an independant German shop, where we'd been doing the mod for years. It was all new to the dealers, and VW eventually came out with a recall campaign to replace the cable from battery to starter solenoid (alternator jumpered from there). The factory cables were actually getting so hot that they wouldn't flow electrons. I got a kick out of the recall notice, because I'd already been doing it to their cars for years.
