professionally I'd recommend mount it somewhere away from the fuse box.
it's all nice and clean until you need to replace a fuse or electrical gremlin come visit you.
especially when you're out and about and you need to check your fuse, you gotta rip the controller off the fusebox and it will be dangling around in the engine bay unsecured unless you have extra tape.
i just dealt with a Lexus GX that kept giving me AC codes, turn out it was the AC relay but the guy had all kinds of junk on the fusebox lid and to get to the relay, everything, and i mean EVERYTHING: bus bars, junkbeam box, fuse blocks, junkbeam breaker, etc all have to be removed. A 15 minutes diagnostic and repair turned into a 2 hours job because of all the junk on top of fuse box lid. Now, imagine doing that on the side of the road/ in the middle of nowhere/ in a parking lot elsewhere.