You can't run more than 4 GPU's in windows as the drivers wont allow it, if you run windows then remove the 6950 or use a linux distro...
I ran 6 GPUs with 11.6 on Windows 7 64-bit this week and it works fine, AMD support also confirmed that 11.6 raised the limit to 8. My biggest problem was that the GUI overclock tools don't seem to be built around supporting that many GPUs, they would run fine but I could not overclock things using the popular tools.