How can I change the byte packing of structures generated from Simulink Coder?

I want to change byte packing of a structure from C++ code generated from Simulink Coder. I have modified cgt file like this but did not work :

%%Code insertion section (required)

These are required tokens. You can insert comments and other tokens in

%%between them, but do not change their order or remove them.
%<Includes>
#pragma pack(push)
#pragma pack(4)
%<Defines>
%<Types>
%<Enums>
#pragma pack(pop)
%<Definitions>
%<Declarations>
%<Functions>

I can't change cfp file because it is not visible, I think Configuration Parameters --> Code Generation --> Templates --> File Customization Template section is not available in C++ code generation.

Any help would be appreciated.

Best Regard Murat