Hi,
In Kamailio we have the concept of double Record-Route to enable us to indicate when Kamailio must gateway between transports and networks. In outbound the flow token is recommended to include an indication of the transport the connection uses and the local address for the connection.
To me this means that double Record-Route is not required for outbound because the Record-Route-URI will indicate the route "out" of the proxy and the flow token indicates the route "into" the proxy.
In fact, I think double-RR should be explicitly disabled when outbound is in use, and that outbound could be "forced" for non-client connections as an alternative to double-RR. Does that make sense?
Regards,
Peter