Funny part is that I wasn't kidding. If it would work on an old C-172 in the propwash, I'd have built one and put it on already. Works like a charm in gliders as many of us know.Love the string, VB.
There was a trailing edge sensor invented for sailplanes, to measure the drag of the airfoil at different flap (camber) settings, so that the pilot could adjust the flap setting to the lowest drag position at any speed. The mechanism was very similar to what you describe, a series of pitot - static holes an inch or so above and below the trailing edge, with the lines plumbed to an ASI or manometer of some sort to display differential pressure.Couldn't one use a remarked ASI as a differential pressure gauge measuring across either a flat plate or upper / lower surfaces of the wing.