Stu, I found it to be trial and error. You need to play around with each of the variables to get it to work right for your tank:
1) The water level in my rear chamber is 5 1/2 lines down. I found this to work best with my system. Others may keep it around 3 lines down or less, but any higher than 5 and mine continually overflows.
2) My air intake valve is set to around 1:00.
3) I tried to lower the skimmer collection cup so that I could close the rear lid, but I have found that it needs to be just a bit higher so I keep the back lid open (probably better for maintaining oxygen levels anyway). I still manipulate the level of the cup from time to time to get more or less production.
And as others stated, it did take a lest a week for it to break in. Good luck.