Results of our grid study to optimize the K-estimator. Left: S/N obtained for each evaluated combination of (a₂, a₃), displayed as a color map. The green area indicates the ‘forbidden’ range where a₃ < a₂. The contours trace S/N increments of 2, slightly smoothed for display purposes. Right: same parameters but for the correlation length r₀, except that the contours again follow the values of the S/N. The blue-red colored circles represent grid points with a₃ = 2a₂ for which the blue-red cylinders in Fig. 3 are equally long. The blue cross indicated our adopted parameter combination for the clustering analysis, as it provides the highest S/N and reaches saturation at r₀.