Cant assume that as it is not straight line math , 4 cfm tests out at 5200 GPM. 4 cfm is also the max for a 2 disc Vertex unit.A single disc from Vertex has a operating range of min .5 and max 2 cfm. So when you see discs that have upwards of 3-4 cfm per disc as the top end or a wide operating range I would be suspect that they are a med slit that may actually lift less at the top end of the range as they start to produce larger bubbles that lift less, That would be an example of when more (air) equals less (lift)Those discs are very popular in wastewater applications as they foul less with wide operating ranges and larger slits.Most waste water units do not need a flow control device since they are mounted level on supply tubes. Onn a pond bottom where you might not be perfectly level the air can go to the high side of the disc without FlowControl which is built into these discs.