Joint inversion for grav and mag

Hi all,

I have been using SimPEG cross gradient inversion code for gravity and magnetics for a while and although it works fine I want to ask:

Is it possible to add borehole data and e.g. a density model as prior information for the inversion to constrain it? Or is there a way to add constraints e.g. covariance and roughness matrixes to manually constraint it?

Best Regards,
Theo