Unconstrained arrays in nested record structures

[Prichard, Jayson]

I am trying to design a nested record structure with each record having an unconstrained array.  Can anyone tell me if the following is possible in Ada/GNAT?  How should this structure be accessed?

 type RECORD_ARRAY_TYPE_2  is array ( INTEGER range <> )
    of INTEGER ;

 type DTED_DATA_RECORD_TYPE is record
    DDR_RECOGNITION                     : STRING (1..1) ;
    DDR_DATA_BLOCK_COUNT         : STRING (1..1) ;
    DDR_LONGITUDE_COUNT            : STRING (1..1) ;
    DDR_LATITUDE_COUNT               : STRING (1..1) ;
    DTED_ELEVATION_RECORD        : RECORD_ARRAY_TYPE_2 ( 1 .. NUMBER_OF_ELEVATION_POSTS_PER_CELL ) ;
    DDR_CHECKSUM                         : STRING (1..1) ;
 end record ;

 type RECORD_ARRAY_TYPE_1  is array ( INTEGER range <> )
    of DTED_DATA_RECORD_TYPE ;

 type DTED_FILE_RECORD_TYPE is record
    UHL_RECORD                      : STRING (1..1) ;
    DSI_RECORD                       : STRING (1..1) ;
    ACC_RECORD                      : STRING (1..1) ;
    DTED_DATA_RECORD          : RECORD_ARRAY_TYPE_1 ( 1 .. NUMBER_OF_RECORDS_PER_CELL ) ;
 end record ;

   DTED_FILE_RECORD : DTED_FILE_RECORD_TYPE  ;

   DTED_DATA_FILE : DIRECT_IO.FILE_TYPE ;

 package DIRECT_IO is new ADA.DIRECT_IO ( DTED_FILE_RECORD_TYPE ) ;

   use DIRECT_IO ;