My settings for X11

HD 6950 2x:

set GPU_MAX_ALLOC_PERCENT=100
set GPU_USE_SYNC_OBJECTS=1
sgminer.exe --kernel darkcoin -o x -u x -p x -I 18 --lookup-gap 2 -w 256 --thread-concurrency 8192 --gpu-engine 910 --gpu-memclock 1250

Hashrate: 2.941 Mh/s (one card 1.47 Mh/s)
WU: 0.021
Temp: 60C in rack

7970 2x:
set GPU_MAX_ALLOC_PERCENT=100
set GPU_USE_SYNC_OBJECTS=1
sgminer.exe --kernel darkcoin -o x -u x -p x -I 13 --lookup-gap 2 -w 256 --thread-concurrency 8192 -g 2 --gpu-engine 1044 --gpu-memclock 1400 --gpu-fan 50-65

Hashrate: 4.05 Mh/s (one card 2.02 Mh/s)
WU: 0.029-0.030
Temp: 57C in rack