There are circles out there that believe overskimming isnt ideal and suggest skimming a tank to its rated volume. ( The Modern Coral Reef Aquarium, Fossa Nilsen )
The only real problem with ovrskimming i see is it taking out more nutrients than it needs to and starves some of the tanks inhabitants. If you are a heavy/target feeder i wouldnt expect this to be a problem. Also as skimming super oxygenates the water that could in extreme circumstances have a negative effect.
I, for one, have a larger skimmer than is required for the simple reason it gives me breathign room if and when i go bigger again and also that i like ot feed my fish a lot.