Trunk mounted battery

I personally don't think these "Ford solenoid" setups are worth doing. You still have to run large gauge wires for the alternator and main power and both of these wires are just as capable of starting a fire as the main battery cable. I just make sure the main wire is routed securely, use grommets and protect from chafing, and inspect it regularly. As for any worst case scenarios caused by a hot wire running through the car, you've already mounted the battery near the fuel tank, what can possibly go wrong?