Wiring help for trunk mount battery

Hyup; I just put a relay in there between the VR and the Alternator.... but you have to break that circuit separately from the battery, else the alternator output will just run around the circle and keep the relay energized. I don't see how it can be done with an SPST emergency shut-down switch.

I bought the FlamingRiver item; beautiful piece, but just 2 poles. I tried to figure out a different way to make it work. But as long as you keep the ammeter working, it can't be done. Me not smart enough to figure it out.
But if you take the factory output from the alt, and remove that wire that normally goes to the ammeter circuit, and instead run that to B+, at the start relay; then install a new wire from the alt output, back to B+ at the battery in the trunk, then when you shut off the battery, the alternator output has no place to go, and Karumba, the engine quits.
The trick is to route that wire in a safe manner such that it can NEVER EVER short to the body.

I suppose, you could make these circuit changes right at the ammeter, now powering up the ammeter from the start-relay, and re-routing the alternator output that was on the ammeter, out to the trunk. I like it.