Marc-8/USM-94 negotiation

Is there any generally agreed upon (PrivateCharacterSet?) way to negotiate a character set of Marc-8 (the character set of Marc21 records, was referred to as USM94 for a while, or something similar) between Z39.50 clients and servers?  Obviously parts of it could be negotiated via Iso2022 if one's willing to give up ANSEL with its undefined final character and can manage to get the right character sets for some of its locally defined final characters, but I was just wondering if anyone is doing this.

Thanks in advance for any information.