yes you can and you can give each card a diff value This is what i run for a 7950 & 7870 on solo mining

 --scrypt -o 127.0.0.1:**** -u **** -p *** --log 1 -E 1 -Q 0 --shaders 1792,1280 --gpu-engine 1050,850 --gpu-fan 100,100 --gpu-memclock 1450,1200 --thread-concurrency 21712,8192 --intensity 19,17 --worksize 256,256 --gpu-fan 100,100