My 55 has 2-K3s that I added on advice from this forum. I went from 2-K1s to the new ones, and the flow seems chaotic to me, but the LPS have adjusted, and the fish are still figuring it out. I have very good flow on the corners now. Not blasting, but flowing. One powerhead is on the left side glass toward the rear of the tank, pointed towards the center of the tank. The one on the right side is mounted on the rear glass, pointed almost directly at the front, but facing a little more to the left. The corners have good, moderate flow, the rear sides have a little slower flow, and the front and center are chaotic, but I think I will like it when I get used to it. Sounds like you have twice as much flow as me, but your tank is deeper. Maybe I should be the one with more flow?