I just tried to tug the knobs off to let you know where the flat sides of the stem is but they don't want to budge.
Good Luck, maybe someone knows how you could set them to flat without the knobs.
Usually, aren't the tone controls considered flat at the exact middle position?
Dean or Mark.........Do you guy's have any idea? []
I keep editing this post. How about posting this question in the technical section?