Help with pump placement

[Pauper]

I have a back left corner overflow in my 140G 30"H tank. My aquascape is two mounds with one on the left and one on the right with room around the perimeter for waterflow. My return is drilled into the overflow so coming in from the top back left. I have your multicontroller with 2 6000 streams and a 7400 electronic pump. I am having problems getting the water to flow well without blowing up the sand. Can you suggest placements for the 3 pumps as well as the heights to give me better water circulation?

 

[rvitko]

I would place the pumps very near the top and use interval 1 and run just one or two pumps at a time with the flow turned down as needed.