Well it seems to me that if the Darlingtons couldn't handle the frequency they simply would not have operated correctly and would have been either full on or just off but the board seemed to turn the wheels fine on jack stands so it seems that they did "handle" that frequency I would think that if it were the frequency to the transistor all would have blown up not just one it seems indicative of over current
I would write in the wiki how to test the comparator and NAND if I knew how and other components. It would be nice if Paul sold the just control board assembled and working. As the mosfet was switched by the control board it sent a positive +12 volts was sent to the bases of the Darlingtions turning them on and off. I still think it would work do you recommend anymore tests?