The Display Size option in the Wings Design Aid's Import Display Files Dialog and Flight Plans' DisplaySize tag utilize the same back-end mechanics to choose either a DS3 or a DS4 display.

How it Works:

When field- or keyword-level DDS lines are conditioned by display size, only those source lines having the same size condition (either *DS3 or *DS4) as the given Display Size value will be processed. For example, assuming *DS4 is the Display Size value used for import: 
      A          R RECORD1
     A  *DS3      FLD1          20A  O  6 42    <-- This line is ignored
     A  *DS4      FLD1          20A  O  8 92    <-- This line is processed

     A          R SFLMSG                    SFL
     A  *DS3                                SFLMSGRCD(24)    <-- This line is ignored
     A  *DS4                                SFLMSGRCD(27)    <-- This line is processed
Note: Formats with OVERLAY or PUTOVR keywords with overlapping rows become members of the EraseFormats attribute for DdsRecord Monarch controls. As the above illustration suggests, the EraseFormats entries for Display Size value of *DS3 may differ from the entries for Display Size of *DS4.