HCN/H₂O MIR blend flux ratios versus 850 µm continuum flux from Andrews & Williams (2005), with indicated error bars. Observations and data collected for the objects (grey hexagons) are compared with the same quantities computed for our model series: disk gas mass M_gas (magenta), inner disk radius R_in (red), power law index of the grain size distribution a_pow (green), flaring angle β (blue), and dust evolution models (brown; symbols are the same as in previous figures). The red and green series extend beyond the shown range and include a_pow > 3.5 and R_in > 5 au.