Maybe I'm not understanding your question? Are you just wanting to just pull data for read only or are you wanting to actually edit the other object? I'm assuming that since you are pulling it into the header, you are just wanting to pull the data for read-only purposes.
Also, Is the field you are wanting to pull specific to CI.Printer for the main CI group object? If it is specific to CI.Printer, you may need to create a relationship between CI.Printer and Incident. Otherwise, you should already have a relationship between the main CI and Incident.