Vertical, flat faces of rock look nice and big from the front, but don’t offer much placement space: if a coral grows outward, suddenly all the blank rock below it becomes shadowed because the coral need only protrude a little to block the light.
Wait til it’s dark and put your phone flashlight above the tank. Use your hand to simulate a coral, and see where shadows are made. Move the phone around to simulate multiple lights, and try to maximize spots that get light from the flashlight, or at least from some directions of the light