Thomas (and all the brethren who watch as he throws his hat through the door!) I do know that you are not getting personal, and I do see the frustration when I come along and say something so outlandish.
It is absolutely true that the state of a fluid flow must contain information on its density, pressure, viscosity and velocity, so we can be sure pressure is an important piece of information, but the lift that the disk sees as the aircraft enters ground effect is NOT a product of a cushion of air under the machine that gives it an extra lift! That old piece of bull called "ground cushion" is an English language statement that does not describe the pressure under the aircraft.
Those great pilots who taught us used this term, the same way we say that your Mom says that you "catch a cold" when you feel chilly after a virus attacks your respiratory system. Your Mother tells you to wear a sweater so you don't catch a cold, a completely wrong medical advice, (the chill you feel is the symptom of the disease you already have, not the cause of the further symptoms you are now guaranteed to get!) Your instructor told you about Ground Cushions, and he was a great instructor, your Mom is a great Mom. Your instructor was not an aero guy, and your Mom was not a Doctor (of course, I now speak metaphorically, your Mom could be a Doctor, and so on, but what the heck....)
I think of the movie "Sand Pebbles" where Steve McQueen tells the Chinese helper about the great steam God in the boiler who gets hot and angry when the boiler is fired. Where does this all end!!