Banktoturn,
Let's recall one of your own explanations:
...The higher the Reynold's number, the more likely the air is to achieve pressure recovery without separating. Thicker airfoils have a bigger variation in pressure over the chord, and so the pressure recovery is more extreme. For this reason, wings operating at lower Reynold's numbers cannot be as thick as wings operating at higher Reynold's numbers without separating. This is why 'good' low Reynold's number airfoils are thinner, and tend to resemble flat plates, and also why flat plates compare more and more favourably to traditional airfoils as the Reynold's number gets small. Having said that, it is the thickness that relates to Reynold's number, not the flatness.
So, the bigger variation in pressure over the chord as you mentioned above is not only because the airfoil is thick but also because the airfoil is far from being a flat plate.
As the Re gets smaller the ideal airfoil gets thinner and also more like a flat plate.
Now we may say that a flat plate is made of straight lines, but a straight line is in fact an arch from a circle, which radius is close to infinitum…
