Somebody came through and emailed me this... while this I assume applies to vessels that are regularly used as UPVs.... this may be an opening that the USCG isn't hard core about "the law" by allowing exceptions.
46CFR26.03-6
§ 26.03-6 Special permit.
(a) If the owner, operator, or agent donates the use of an uninspected passenger vessel to a charity for fundraising activities, and the vessel's activity would subject it to Coast Guard inspection, the
OCMI may issue a special permit to the owner, operator, or agent for this purpose if, in the opinion of the
OCMI, the vessel can be safely operated. Each special permit is valid for only one voyage of a donated vessel, which is used for a charitable purpose. Applications are considered and
approved on a case-by-case basis.
https://www.law.cornell.edu/cfr/text/46/26.03-6