Why does everybody insist on interrupting the positive terminal of the battery? This is a horrible way to interrupt the power of any 12VDC electrical system.
The only reason to interrupt the positive terminal is if you only have the one main set of terminals, which would require running the alternator to the positive battery terminal and then interrupting both.
If you are willing to spend the extra ten bucks on a shutoff switch with a secondary pair of terminals, it is infinitely safer to interrupt the negative terminal. In order to shut the system down you could... you know... use the same damn line that you otherwise normally shut the engine off with (like, you know... the IGNITION switch!) and run it in series with the secondary switch.
All these extra provisions for load dump resistors and what not are completely unnecessary. It's way easier than you think.
The best part about interrupting the negative terminal is the failure mode. If the negative battery terminal comes off the switch and / or is shorted out in an impact, you've done nothing more than complete the normal circuit. Big whoop. If you were instead switching the positive terminal, you suddenly have a MASSIVE fire risk as you battery cable is now arc welding itself to your cage.
The Pentastar whisperer