I know that once upon a time, the Maw had black holes at its hyper entrance points, but the Powers That Be decided that was a little too dangerous, and the entrance points were cleared of their black holes.
I'm wondering if all black hole systems are the same way, in that you can hyper into that system from at least the four corner, and maybe the sides, without worrying about immediately being swallowed up by a black hole.
For example, Galactic Center has 9 holes, and the Tyus Cluster has 5. Would it be safe to visit those systems, and know for certain that there won't be a black hole at the entrance points?
Yeah back when I was making the new systems with blackholes I made sure that there were none at the entrance (heck none on the outside edges at all) and there was at least 1 non-grav well covered square to allow you to exit.
As for hidden systems, I don't know but I presume the answer would be possibly.