  We present mass models for a sample of 30 high-resolution rotation curves of
low surface brightness (LSB) galaxies. We fit both pseudo-isothermal
(core-dominated) and Cold Dark Matter (CDM) (cusp-dominated) halos for a wide
variety of assumptions about the stellar mass-to-light ratio. We find that the
pseudo-isothermal model provides superior fits. CDM fits show systematic
deviations from the data, and often have a small statistical likelihood of
being the appropriate model. The distribution of concentration parameters is
too broad, and has too low a mean, to be explained by $\Lambda$CDM. This
failing becomes more severe as increasing allowance is made for stellar mass:
NFW fits require uncomfortably low mass-to-light ratios. In contrast, the
maximum disk procedure does often succeed in predicting the inner shape of the
rotation curves, but requires uncomfortably large stellar mass-to- light
ratios. The data do admit reasonable stellar population mass-to-light ratios if
halos have cores rather than cusps.
