first and foremost -d 0,0 breaks currently because it operates both threads in the same CUDA context,
and you will get some non-validating hashes (the threads will step on each other's toes). This is fixable,
but only with an update to ccminer.

With two GPUs, I'd recommend to run a bat file with -d 0,1 twice on the same PC.  The total hash rate
of both instances would be more than the hash rate of a single instance running - mainly because of
higher overall GPU utilization.