My problem was separating HL7 messages by message type.  I had to create multiple File Operations.  So I with custom code I am able to use 1 File Adapter for 1 interface and multiple message types.  I did experiment pulling the MSH 4 out of the raw content to further access dynamic information, but that may open a need for more robust error checking / lookup default actions.

Using the recommended naming convention of "To_FILE_<IntegrationName>"

I decided to use a generic file name and path in the default settings.