Sorry Almost for straight up criticizing you and your idea. I should have offered constructive criticism instead. So....IMO this will never work. Why...because corals like to grow like they please.....yes you can manipulate some but you will never be able to get 3 perfect rectangles side by side of different corals...especailly monti caps...which is a poor choice considering they grow up and down (plating). Also like I mentioned....in all my years I have never seen a healthy white montipora.
But....if you dont agree and feel you can prove me wrong than post a picture.