This was generated by javafoil. See: http://www.mh-aerotools.de

If you can get software such as this to dump the pressure distribution you can put a number on the net force applied to the control surface.

Note the streamlines (lines of constant speed). When I ranted about change of momentum, I was taking about this. The change in velocity (speed and direction) of the flow represents a change in momentum.... which can only be caused by a force.... the lift and drag. That was I was trying to get you to recognize. But you are likely better off sticking with the pressure distributions as has been noted.

Reality will be more complicated that this picture. As mentioned, the flow may separate, etc, etc, etc,.