Some confusion about building a device model

[TombInSeeper]

The instruction only describes "choose weight_factor to make the curves for diff rd/wr ratios overlap. " Is there a more precise way ? If I have multiple values of write weights that make these curves overlap, such as 4.5, 4.6, and 4.7 , how should I choose them? And when I weighted the writes using a linear weighting method, I found that < weighted IOPS, delay > composed of ground scatter points did not converge well on a curve.