I have to agree with the corals need for laminar flow. I think that is more important that the constant back and forth, but the laminar flow has to be from multiple directions to avoid undesirable growth patterns. You don't see much SPS in the tidal zones, they tend to be below any wave action. So, that being said, I also have mine in a clockwise fashion, with the rockwork more in the middle to keep the 2 flows (front and back) separate.

The corals will grow into a plane of water to disrupt it for its optimal usage.