I have a 5TB drive plugged into the sole USB slot on my AirPort Extreme but it's on it's way to being filled. I'd like to add a second HDD but am unsure what concerns that may present. Anyone used this setup? Limits to size? Hardware considerations? I'm aware I could get a NAS but I'm planning to do that in the future to act as a DVR and would prefer to keep them tasked separately.