I have them overclocked to 900 MHz. Mem downclocked to 600MHz. Unlocked shaders. Using -v flag, and -w 256 as well as -f 1.
I was getting 400mh/s, now I get 300mh/s. Config hasn't changed at all. I have had 2 7970s and 2 6950s in the system and the cards dropped in speed without any hardware configuration change.
Was the system running the the 7xxx cards before, and now is running the 6xxx cards without changing the drivers or SDK versions?
What drivers and SDK are you running them with right now?