Placement of Powerheads?

[Lampshade]

Depends on rock placement a lot, I have my rock in islands in the center of the tank. I point one large power head across the front of the display, and one across the back. My smaller power heads i use for trying to keep some flow through my rocks. This seems to work for me, the small powerheads kick up detritus from rock work, and the large power heads keep the detritus suspended in the water until it's taken by the overflow.

It took months of adjsutment, and i still play with them frequently when i notice area's with little flow