Pitching moment as a pure moment and its measurement with a homemade force balance
There are better physicists than I at this site, but seem to remember a solution proposed in a wind tunnel test with load cells as follows:  Do the measurements separately.  

Lift could be measured at the center of lift using only support 1.  C lift could vary with AOA (data points are generated one at a time from C lift at a given AOA).

Pitching moments could be measured using support 2 only, with the wing pivoting on its AC
(which could be some type of axle).