While looking at my tank, 15" is still too big I think for a return section. Need to find out a way to work with I got. Might end up buying a skimmer before I build the sump just so I know things will fit, but I do know the skimmer has a 14x9 footprint. I'll also either be using a magdrive24 or a quietone 4000 return pump......Depending on the water levels I wonder if I could build the skimmer a stand and let the pump sit beneath it. Off to do more reading on skimmers!! Let me know y'all think.