I just completed my 40B/20L sump build. I used a modular marine ghost overflow and drilled two 3/4 inch returns high on either side. I put both up high jusy incase of a power outage they will break siphon quickly and my sump will be able to hold that extra water. Here are a couple of pictures. In the close up shot you can barely see my overflow because I painted the back black.
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