Size of objects in records with an array.

["Richard Charts" <richard.charts@gmail.com>]

So I'm having more fun with records in Ada, particularly ones that must
be of an exact form.
I have a 32 bit data item I'd like to access the individual bits for.
My initial way was the 1st blurb below.  It works but reality slapped
me in the face when I realized I needed to access the bits either like
an array or with some way to loop through the bits.
So I tried the bottom way, but it says the size is incorrect.  Is there
a way to make this work, or am I stuck looping and bit shifting a 32
bit item?
Thanks.
-------------------------------------------------

    type Data_Msg is
    record
        A429    :   Interfaces.Unsigned_8;
        Bit9    :   Boolean;
        Bit10    :   Boolean;
        Bit11    :   Boolean;
        Bit12    :   Boolean;
        Bit13    :   Boolean;
        Bit14    :   Boolean;
        Bit15    :   Boolean;
        Bit16    :   Boolean;
        Bit17    :   Boolean;
        Bit18    :   Boolean;
        Bit19    :   Boolean;
        Bit20    :   Boolean;
        Bit21    :   Boolean;
        Bit22    :   Boolean;
        Bit23    :   Boolean;
        Bit24    :   Boolean;
        Bit25    :   Boolean;
        Bit26    :   Boolean;
        Bit27    :   Boolean;
        Bit28    :   Boolean;
        Bit29    :   Boolean;
        Bit30    :   Boolean;
        Bit31    :   Boolean;
        Bit32    :   Boolean;
    end record;

    for Data_Msg use
    record
        A429    at 0 range 0..7;
        Bit9    at 1 range 0..0;
        Bit10   at 1 range 1..1;
        Bit11   at 1 range 2..2;
        Bit12   at 1 range 3..3;
        Bit13   at 1 range 4..4;
        Bit14   at 1 range 5..5;
        Bit15   at 1 range 6..6;
        Bit16   at 1 range 7..7;
        Bit17   at 2 range 0..0;
        Bit18   at 2 range 1..1;
        Bit19   at 2 range 2..2;
        Bit20   at 2 range 3..3;
        Bit21   at 2 range 4..4;
        Bit22   at 2 range 5..5;
        Bit23   at 2 range 6..6;
        Bit24   at 2 range 7..7;
        Bit25   at 3 range 0..0;
        Bit26   at 3 range 1..1;
        Bit27   at 3 range 2..2;
        Bit28   at 3 range 3..3;
        Bit29   at 3 range 4..4;
        Bit30   at 3 range 5..5;
        Bit31   at 3 range 6..6;
        Bit32   at 3 range 7..7;
    end record;

    for Data_Msg'size use (8 * 4);

--------------------------------------------------
But I want to use this:
--------------------------------------------------
    type Bit_Array is array ( Natural range 8..31)
        of boolean;

    type Data_Msg is
    record
        A429    :   Interfaces.Unsigned_8;
        Bit_Arr    :  Bit_Array := (others => false);
    end record;

    for Data_Msg use
    record
        A429    at 0 range 0..7;
        Bit_Arr    at 1 range 0..23;
    end record;
    
    for Data_Msg'size use (8 * 4);