How many sides vieawable will the tank be?
I like the idea of a center overflow right in the middle of the tank (say 3"x3" and use the smaller Stockman style standpipes) and have your returns coming up through the bottom of the tank. The only problem with something like that is it is harder to aquascape and hide the overflow.
With an external overflow (with the glass notched out) you don't tank up any room within your tank. Therefore you have the full inside dimensions of the tank to work with for aquascaping. IMO it is a much cleaner look having only a little notched area in the back glass vs a partition in one of the corners.
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32"x32"x20" Cube-ish tank
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