Just out of curiosity at what intensity do you run those 7950?
Im using I 19
Have you tried lowering that a bit?
18 or 17 and see what happens with the rejects... or even better use Kalroth version of cgminer xIntensity 4 with 2 threads... as already mentioned somewhere in this thread?
My 7950 undervolted gives 0.5% reject rate 620 kh/s with those configs and I'm sure there are better ones out there!
Either way, as BombaUcigasa said, it IS profitable