Interesting that the relay is that high current rating. I did not pay any attention to this when I wired mine. But I added a 100 amp water proof circuit breaker right off the battery for all of my accessories to hopefully resolve a short circuit. Then they are wired through the normal 20 amp fuses etc on the switch panel. Bought the 100 amp circuit breaker at O'relleys for around 20 bucks.
I have a lighted accessory panel that I left hot. So when the key is off, this is still on, hot, intentionally.
Matt, why would you add a second relay? Is this to a new fuse panel? Just wire the one lead to a switchable hot and use the switch? If I am thinking correctly. And think about this for awhile before you drill holes in the vehicle on what all you are going to do. What may be a nice center spot may have should have been pushed to the side to allow room for another switch.
So far, I have dome light switch, GPS switch, 2 way radio switc, and going to wire my backup lights maybe into a switch. The front D2 Duallies I used the factory switch and breaker.