Mercury’s own cable is only about #4. Most of the time, you see a half volt to a volt drop in those cables when everything is working right. The 4/0 is just recommended because that’s the most the switch can take, I would think. I bet if you used #2 over 12 feet, that would be plenty.If you want to see it in Black and White, Maybe ABYC has online technical specs that you could check.
Long live American manufacturing!
