Rats! 
First decent winds since the change over and the current combination is clipping at around 16Hz in practice, well below the theoretical 72Hz. So, any rotation above the high 30’s in mph is getting clipped. The result is apparent “1 minute” wind speeds of around 5mph during a gale!
Edit: I’ve just added an image to illustrate the positions of the capacitor and resistor in the circuit. I’ve also shown the 1 M ohm restor that Eric mentioned. I’m not at all clear how that might be affecting matters…
