a) The model fitted to the SED of BD+61154 with all the model contributions: interior layer (blue medium sized dashes), surface layer (red short and medium sized dashes), inner rim (pink dotted line), star (green short and large sized dashes), and total sum of previous contributions (black solid line). b) The SED changes when one varies the value of the maximum grain size in the interior layer (a_max). The inset shows the projected dispersion curve (see Eq. (1) for the definition of the dispersion χ) when only a_max varies, all other parameters being fixed at their best-fit values. c) The same as b), but varying the outer radius. d) The same as b), but varying the disk mass. The x axis of panels b) and d) has been reduced to λ > 100 μm, were the SED is more affected by a change of the parameters a_max and disk mass, respectively.