Varying Length fields, and LikeRec

I am writing to a file, and one of the fields is a 150 Alpha VARLEN
field.  This file will contain a large number of history records, and
I am doing this to conserve space:

     A            DMESSAGE     150A         TEXT('Denial Message')
     A                                      VARLEN

What I am trying to do is create a DS, using LIKEREC with the format
of the file which contains the VARLEN field, like this (this is just
some test code):

     FCBI1PF    O    E           K Disk

     D TheTest         DS                  LikeRec(RCBI1:*Output)
     D                                     Inz

The DS that gets created contains a field for the DMESSAGE field, and
it is set up as VARYING by the compiler.  Beautiful.

Unfortunately, when I eval something into the DMESSAGE field in the
data structure, then write to the CBI1PF file using that data
structure, like this:

TheTest.DMessage='This is a test message, created for testing purposes';
Write Rcbi1 TheTest;

In debug, I see that the DS has the correct length set (52) using %Len
to test the length.  But when I write, the field in the DB file
contains all 150 characters, with trailing spaces added.  Is there a
trick to making the WRITE op recognize the DS variable length, that
the compiler created for me, based on the file structure, or do I have
to eval %Trim from the DS to the actual file buffer fields?

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