I run additional inline fuses just prior to the 2nd battery, as close to it as I can, and then fuses to the amp, as close to the amps as I can. If your not running your wire through the metal to the rear area then probably no need. I really don't know why I did that either, I used huge, thick nylon grommets to go through the undercarriage already. My cable is run under the car and in the event that something really big and sharp cuts into the cable under the car, the fuses just prior to the battery will prevent an issue should they short out. If you are fusing the rear cable, then just prior (within 18") of the lead into the 2nd battery is recommended. If you are not running 2nd inline fuses/breakers to the rear battery near the battery in addition to the ones under the hood, then the fuses for the amps should be as close to the amps as they can be.