Parameter combinations of inner disk radius R_in and the radii of the smaller and larger grains a_S, a_L for the system HD 172167 (see the Fig. B.1 for all other investigated targets). The blue sections enclose all parameter combinations able to reproduce the flux densities inferred from observations in the NIR and MIR wavelength ranges. The red sections indicate parameter combinations that cannot reproduce the observations. The upper boundary of possible values of R_in is given by the distance, where the radiation originating from the grain population of smaller grains no longer shows a NIR-to-MIR flux density ratio (Eq. (4)) higher than the observed value (Eq. (3)). The lower boundary is given by the physical scale corresponding to the IWA of the KIN, which is depicted by the solid black line. The dashed black line depicts the sublimation radii for different grain sizes. The intersecting set of parameter values for which, on the one hand, the dust configurations can reproduce the observations and, on the other hand, the dust grains of the respective grain sizes do not sublimate is indicated by the dashed area. Right: parameter space of R_in and a_L for all possible values of a_S. Left: parameter space of R_in and a_S with the value of a_L fixed to a_L ∈ {10 µm, 100 µm, 1000 µm}; valid parameter combinations of R_in and a_S are the same for these three values.