I have 4 7950s and I pull ~640 kh out of each card with these settings.

cgminer.exe --scrypt -o stratum+tcp://eu.wemineltc.com:3333 -u user -p pass --shaders 1792 --gpu-engine 1100 --gpu-memclock 1625 --gpu-fan 100 --thread-concurrency 21712 -I 20 -g 1 -w 256

That said my pay per round is about half of what the estimated actually is, its like only ~1400 kh are actually making it through to the server.  Any idea why I am only earning around half of what any calculator is suggesting?