Including header and accessing classes' effect on release exe’s performance and size in VC6

I want some guidance on how to set up my classes to optimize my program’s speed and size.  I don’t really care about compile time.

My program has alot of large classes with large header files and most new classes I make need one or two functions from at least a dozen of the large classes.  
They are usually the same functions needed across the project.

For example:

class CMyApp : public CWinApp
  CString TempDirectory();
…(Tons of other functions)

A crapload of other classes need that TempDirectory() function, will it hurt the program’s performance to have “#include “MyApp.h” all over the place?

Should I add some intermediate files to provide access to these common functions?

For example:

CString TempDirectory();
…(a few other common functions)

“#include “MyApp.h”
CString TempDirectory(){
      return (CMyApp*)AfxGetApp()->TempDirectory();
Then just include “Directories.h” everywhere.

Any suggestions and explanations would be appreciated; the project is becoming a mess of header files.
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>>A crapload of other classes need that TempDirectory() function, will it hurt the program’s performance to
>>have “#include “MyApp.h” all over the place?

I don't see a reason to do so:

CMyApp* pApp = (CMyApp*) AfxGetApp();

CString strDir = pApp->TempDirectory();
bigsteve87Author Commented:
That was one example, but there are alot of other similar cases.

If I use CMyApp* pApp = (CMyApp*) AfxGetApp(); in a class that does not have “#include “MyApp.h” in the cpp file, I get an error because it does not recognize the class CMyApp.
>> Will it hurt the program’s performance to have “#include “MyApp.h” all over the place?

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bigsteve87Author Commented:
Ok, good.

So the compiler should ignore the functions that are not used?
This has minimal impact on compilation time, but doesn't affect runtime. Assembly code generated by compiler contains only call this this specific function, nothing else.

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For example, every Windows application has line:
include <windows.h>
which contains thousands of Windows API. Compiler needs some time to scan this file, but executable module contains only calls to API which are actually used, and not to possible Windows API.
bigsteve87Author Commented:
Thanks.  I wanted to make sure that I wasn't unnecessarily bloating my program.
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