Resulting reduced χ² distributions from a comparison between our model grid for the 69 μm forsterite feature as a function of iron fraction and grain temperature, and the Herschel-observed bands in eight of our targets. Our model grid is an interpolation based on several different measurements of both optical constants with the DHS shape model and with absorption coefficients. Thus no fixed grain size can be given. Where applicable a grain size of 0.1 μm was used.