Use custom BibLaTeX fields with Org-ref

Question

I am managing my bibliography with John Kitchin's org-ref package. I want to create an @film entry type with a few custom fields. So in my init.el file, I have:

;; Create fields for Film type
(add-to-list 'bibtex-biblatex-field-alist
  '(("director" "Director(s) of a film, video or DVD title")
    ("producer" "Producer of the film title")
    ("distributor" "Distributor of a film title")))

;; Setup Film type
(add-to-list 'bibtex-biblatex-entry-alist
  '("Film" "Film, video or DVD"
    ("title" "year" "type")
    nil
    ("director" "producer" "distributor" "address")))

;; Use BibLaTeX to process your bibliographies
(bibtex-set-dialect 'biblatex)

Now the question remains as to how I should tell org-ref that "director" and "producer" should be treated as authors and "distributor" should be treated as a publisher, when producing the citation?

For the author aliases, the BibLaTeX Manual recommends something like this:

\DeclareLabelname{%
  \field{director}
  \field{producer}
}

But adding #+latex_header: \DeclareLabelname[film]{\field{director}\field{producer} to my org document does not have any effect?

Is there perhaps another bibtex.el variable I should customize?