I'm planning either a 5 1/2 or a 10 (haven't decided yet) and while I won't be using an MJ 1200, I will be using 2 or 3 mini tunzes as a closed loop. To do so, I'm placing a piece of acrylic as a false back wall and drilling the acrylic. Think of it as a nanocube in a 10 gal AGA with more space for a fuge and more inlets for a more diverse flow pattern. Perhaps more work then what you were looking for, but it is one way to create a closed loop with a powerhead without having to drill the back of a glass tank...plus, you can hide all of the stuff like you would in a sump.