Just edit the cgminer.conf file and set whatever freq you want.
What directory is this file in? After editing the file, do I restart the miner?
My batch 1 Z9's made it really easy to change the freq from the drop down under advanced config, these batch 2 miners, at least the ones I got, only shows "balanced" under advanced config, so they are hashing at 50% less than my batch 1 Z9's.