According to Escobal in Aquatic Systems Engineering: Devices and How They Function, the upper limit of air injected into a skimmer is 13% of the water volume inside the skimmer. More than that and the additional air causes the micro bubbles in the skimmer chamber to burst and form larger, less efficient bubbles.
The hard part of this from a practical standpoint is figuring out just how to determine when you have the air/water ratio correct. I think the best way to do it is to shut off your air pump and mark where the water level is, and then dial in enough air so the water line raises to a level 13% higher than before (multiply the water level by 1.13 to find the level with air). If you have a square mixing base at the bottom of your skimmer, you could dial a little bit more to make up for the extra volume in the base.
I have a feeling that a lot of you will end up using much less air than you were before, but this is where the skimmer should be running at maximum efficiency. You may have trouble getting the foam up and out of the neck on taller skimmers. In this case, either increase the water level in the skimmer or cut down the riser tube until you get the dryness of foam you're looking for.
Mike