Best way to persist msg.res and msg.req in a flow which uses a Websockets to connect to another node instance

I'm trying to connect two node-red instances, (DMZ/LAN) using Websockets, I'm having some issues when using the connection with http requests.

the DMZ node-red instance has a http in /echo
the message is then sent via a Websockets to the LAN node-red instance, who replies.
I see the correct info in the debug window returning, however, the 'new' message doesn't have the original's msg.res and msg.req and so can't reply.

What is the best way to persist original msg.req and msg.res all the way to the http response?, or to "merge it back to it's original _msgid?