I'm limited to how much flow I can have in the tank because of them. ATM I'm running a mag 9.5 as return and two Koralia 1's. This gives me about 30x per hour, any amount more would cause everything to blow around too much.
I'm surprised that grow-out in suspension isnt more popular. By doing this I dont have to custom make a shallow tank to efficiently use as much of the volume as possible. I hang all of my SPS and then litter the bottom with LPS and softies. I guess the real catch is that its a pain to reach down to the bottom of the tank with everything hanging in the way.