My bad. Recent amendments (Dec. 28) to 28 CFR part 75 (the regulations that clarify 18 CFR 2257)
do allow 3rd party maintenance of records. See:
§ 75.4 Location of records.
Any producer required by this part to
maintain records shall make such
records available at the producer’s place
of business or at the place of business
of a non-employee custodian of records.
DATES: This rule is effective January 20,
2009. Compliance date: The
requirements of this rule apply to
producers of visual depictions of the
lascivious exhibition of the genitals or
pubic area of a person and producers of
simulated sexually explicit conduct as
of March 18, 2009.
See Federal Register / Vol. 73, No. 244 / Thursday, December 18, 2008 / Rules and Regulations