I think there are lots of places to anchor between Altmar and the compactor. There are also several places where your boat will run over the shoetops of the Wade anglers because things pinch in tight. Not sure of flow minimum because I'd rather eat a pound of my own crap than fish there. Thinking it has to be 700-ish to get a boat through. There are tons of braids and islands, if you are not familiar with where you're going oh, you may get your boat stuck and have to walk it back 1/2 Mile. Make sure you look at a map before you even think of pushing off.
I have a buddy who's been up there fishing for weeks. Two fish. That's pathetic. Wouldn't waste gas or my time to freeze and catch a measly fish or two
Like mentioned before, going below the compactor will be a problem and not recommended.