According to the charts with a cya level of 60, my min FC is 5 and target FC is 7. Is there any reason not to run it on the high side? Maybe consider 7 as the minimum and try to keep it floating between 9 and 12?
The cost should be the same to bump it up a few points whether it is from 5 to 8 or 9 to 12, and I would feel a little safer considering my month long fight with mustard algae. I also think it would compensate for any errors I may have made reading the cya test.