INS_HNTCH_REF and/or INS_HNTC2_REF = hover_thrust * SQUARE(min_freq / hover_freq)
Should look at /analysis the pre-filter data.
More challenging if you face multiple peaks.
if the autopilot is capable of running the FFT (most F4 based autopilots are NOT), then by enabling the FFT_ENABLE and using the RC Auxiliary function “162” (Auto Throttle Notch Setup) during a sustained hover, the center frequency, INS_HNTCH_FREQ, INS_HNTCH_ENABLE, and INS_HNTCH_MODE will automatically be setup for the first notch, avoiding log analysis to determine center frequency as outline below: