is there a way Bfgminer can use different Frequency to different miner?

i found one of mine should use 232 and other should use 224 for get best hash rate / power usage, about 19M and 460W total
when i use 240 to both, i get 18M and 500W total

EDIT: found it

-S zus:/dev/ttyUSB0 --set zus:chips=64 --set zus:clock=236 -S zus:/dev/ttyUSB1 --set zus:chips=64 --set zus:clock=224