Median values of the dPIE truncation radius r_cut vs. the characteristic dPIE central velocity dispersion σ₀ for the galaxies that perturb the strong lensing system of Abell 611. The red triangles show the results obtained linking the galaxy parameters to the same scaling relation in the lens modelling (Case 4 in Table 5), while the blue stars represent the results obtained optimising the galaxies individually (Case 6 in Table 5). The grey dashed lines show the iso-density contours. The error bars indicate the 1σ uncertainty, while the cyan boxes indicate the 3σ confidence region for the results which refer to Case 4.