JB -
I installed a single corner overflow in my 150 (72 x 24 x 20) and am very happy with it so far. From your diagrams, my overflow is very similar to what you're planning albeit on a slightly smaller scale; 13 x 6 as opposed to your 18 x 9.
I planned the tank out this way mainly for aesthetics, but it's performed well to this point. What are your reservations?
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