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…
adam_one,
It seems to me that, as I have mentioned before, the confusion is between 'thin' and 'flat'. The severity of the pressure recovery increases with maximum thickness, not as a result of thickness variation. This is why airfoils with smaller maximum thickness tend to be more favorable at low Reynold's numbers. This in no way implies that a constant thickness is favorable for low Reynold's numbers. The point I was making in the text that you quoted is that a thin wing bears a visual resemblance to a flat wing, since the curvature on the top and bottom surfaces is less visually obvious than it would be on a thicker wing. I conjecture that this visual resemblance is part of the reason for the apparently common confusion between thin wings and flat wings.
My contention is quite simply that the 'optimum' airfoil, even for low Reynold's numbers, is one with varying thickness along the chord, even if the maximum thickness is small. If someone can explain to me why performance of a constant thickness airfoil is optimum in some range of Reynold's numbers, I'd certainly change my thinking.
banktoturn