[CentOS] Centos 5 32-bit vs 64-bit question

I'm trying to install a custom greeter into a newly installed 64-bit 
Centos 5 system.   I originally tried to modify Xsession to include xpop 
/path/to/text_to_dispay as the first executable line, but that didn't 
work.

Then I read about gdmconfig which led to gdmsetup which led to 
custom.conf.

Nothing, so far, is producing a custom banner prior to login.

Is this an issue with CentOS 5, an issue with the 64-bit version, or 
something else I need to learn?

Thanks.

Scott