I think we should have getHalfLightRadius be accurate, similar to what you do for getFlux.  I think what `flux_untruncated` should mean is that the input `half_light_radius` and `flux` parameters correspond to the untruncated profile.  But then the profile is truncated after that calculation is done.  (This is what you already did.)  But then the get methods should return the true values in both cases.  If people want to actually do something useful with the returned getHalfLightRadius value, I think it probably ought to be the right answer.