You know, I am the wrong person to ask, but I have a skimmer rated for 200 gallons on a 55...I just keep the flow down a little lower, and I have had no problems.
I think if you skim too much though, you can drag out a lot of nutrients and trace elements that are actually needed by the corals...but I am sure you can control this by proper settings of the skimmer.
I'll bump it, and hopefully someone more experienced can tell you.