Hmmm saltwater tanks usually have the drills closer towards the edge... I have an idea though. You could make standpipes, get driftwood or rock or some other decoration, and drill the decoration so that the standpipe fits inside, this way you have a hidden standpipe, and then you could close up the 4 small holes and have your return pump set to return over the back.
If you do not feel like going with this route, you can buy overflow boxes that hang on the back of the tank and just close up these holes.