Swap Writer for CFD (FIX v4.2)

Is there a standard way to present the swap writer for a CFD? Perhaps tag 439 [SettlingFirm]. Most places seem to use tag 1 [Account] but that just seems wrong as there are so many other potential uses for that tag & it would be nice if it had its own home! We are finding it common for Asian brokers to want to know pre-trade i.e. on NewOrderSingle who the writer will be. Any suggestions or known consensus much appreciated?

Actors and accounts can be provided with the Parties component (see PartyRole(452) for valid values). Account(1) should only contain an account number. AccountType(581) can be used to describe the nature of this account. But there is only one instance of Account(1) whereas the Parties component can have any number of instances.