The way that I have my closed loop on my 210 is as so.
I have two overflow boxes and that works off of one pump. The return is "T" off and distributes water to both returns. Then, I have 3 holes drilled in the back of my tank, dead center. One of the holes, the one in the middle, is the drain, while the two on the sides, are the returns. This works off of another pump that I have the plumbing "T" off on.
I have included pictures for you. The two black lines in the first pic are the returns of my closed loop, and the red line points to the drain. The water drains directly to the pump, and comes directly back up to the tank. It does not go anywhere between.
The last pic is how I have hid the closed loop so that you cannot even see it, yet, still pumps water all the way to the front of my tank.