I don't think you will find anything in writing to answer your question. The only thing you might hang your hat on is that the CTR calls for a street address. Including c/o in that field is not a street address. Just keep one thing in mind. The purpose of the CTR is to report large cash transactions. If IRS is interested in following up on a CTR, they want an address where they can go to get records and find someone with knowledge of the transactions. I think the street address is sufficient.
Politicians are like diapers. They need to be changed often and for the same reason.