How do you add difficulty at suprnova?
z-enemy -a x16r -o stratum+tcp://rvn.suprnova.cc:6667 -u your_Login.your_worker_name -p x -i 20
Is this correct: z-enemy -a x16r -o stratum+tcp://rvn.suprnova.cc:6667 -u your_Login.your_worker_name -p x -i 20 -d 16
?
No, this would mean that you are mining only with your 16th GPU (out of 16+).
Not sure if you can set difficulty for suprnova in your bat file unless they have different ports for high & low diff. I can't see any info about this on their rvn hompage.
I thought as much

Suprnova is the best place for RVN and we can't even make use of the "Search mode"
What about: z-enemy -a x16r -o stratum+tcp://rvn.suprnova.cc:6667 -u your_Login.your_worker_name.DIFF_16 -p x -i 20
I've seen that done on some pools with the username set up.