Notes. For each model, we show the best-fit values of the parameters, the number of degrees of freedom (ndof), the minimum chi-square (χ_min²), and the rms values. The values of the x and y coordinates are referred to the center of light of the main elliptical lens galaxy, i.e., to its brightest pixel. The position angle, θ, is measured counterclockwise from the x axis, aligned following the horizontal direction of Fig. 1. We report in the table only the values of the optimized parameters, while for each group member we fix its total mass center to its luminosity center (≡(0, 0) for the BGG), and the axis ratio and core radius values to q = 1 and r_core = 0, respectively.