Are you breaking up your message into multiple messages inside the pipeline and need this on each message?
If not, then you could just put them both inside the same schema and promote them.
If you are breaking it up, not sure if you can create a property schema on the header and promote them. I thought you could – but someone told me you couldn’t. It would be worth a try I think. Otherwise, I would think you could do this inside a custom pipeline to promote the values.