I use these settings in my batch file for my 7950's and they are working great: (adjust them according to your cards )
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
del *.bin
ultracoinminer -o stratum+tcp://ultra.nitro.org:3337 -u stuhlman.1 -p 1 --scrypt-jane --sj-nfmin 4 --sj-nfmax 30 --sj-time 1388361600 -w 256 -s 1 -E 10 -I 19 -g 1 --thread-concurrency 24000 --auto-fan --queue 0 --temp-target 70 --temp-overheat 80 --gpu-fan 75-95