Ground-based optical spectra from the GTC (in dark grey; Cooper et al., in prep.). These spectra have been simulated from the original spectra by passing through MIOG. The object short names are: J1717+6526 – L6, J1213-0432 – L5, J0453-1751 – L3, J1745-1640 – LI, J0935-2934 – LO, and J0938+0443 – M9. Over-plotted are the corresponding observed RP spectra of the same objects coloured by effective temperature and labelled by spectral type. All fluxes are normalised by the area and linearly offset.