How do you 'map' a field in the MailStream Plus input records so it will be in the output records?

MailStream Plus™, all versions, all platforms
Question: A user had data fields in the input records that he wanted to 'map' so that the data fields would also be in the output records after the presort, such as account numbers, etc.

Answer:  Mapping of such fields is not required.  Some fields are mapped in MailStream Plus™ (MSP) that are used during the presort, such as where the ZIP Code and Carrier Route info is.  

But regardless of whether a field is mapped or not, all of the data is transferred to the output records providing that the output record length is sufficient.

For example, if the input records are 200 bytes long full of data, all 200 bytes are automatically copied over to be in the output records. 

Keep in mind that the MSP job will have a CONTRL parameter, and probably several POSTxx parameters, and maybe IMBxxx parameters that will post data into the records.  The job would need to be setup so that the posted data is not put into locations that have customer data that should not be over-written.  
So the job parameters may need to post the data into locations past the length of the input records.  If so, then the output record length on the FILEDF MSNAON should be suitably increased (and the LRECL in the JCL on z/OS mainframe platforms as needed).

For example, this is the FILEDFs and lengths of the records in the IVP test job that comes with MailStream Plus.
FILEDF MSSTIN   L 0192  length of input records with customer data in 1-192
FILEDF MSSTOR   L 0192  length of reject records (bad ZIP Codes, etc.) same as length of input records
FILEDF MSSTON   L 0292 MSP temporarily adds 100 bytes to the front of the records for internal processing, so you have to allow for it. 
FILEDF MSNAIN   L 0292  same length as the MSSTON file, and MSP now removes the 100 bytes it had added to the front of the records.   
FILEDF MSNAON   L 0550  output record length, because in our test job we post new data into the records after byte 192.  But bytes 1-192 are the same as they were in the input records.  (Unless in your job you choose to have MSP post something into that area.)
UPDATED:  May 15, 2019