>Another thing about this. I think the bandpass files you included for LSST could be pre-truncated.
Yep.  I think some of the SED files also go to ridiculous wavelengths and could be pre-truncated
>... and I think thinning it out a bit could help speed things up.
I think I recall getting about the same results for 10A binning as for the default LSST 1A binning.  I'll verify and thin if it makes no real difference.