How/Where can I specify the HTML template (for signin page) file instead of signin.html ?

Would like to customize PeopleSoft signin page with not signin.html (such as Z_signin.html cloned from signin.html file ) .

Would you please help me understand how to customize PeopleSoft signin page without modifying signin.html ?

<Background>

Although I tried it the following steps, it did not work fine for me.

1. Copy signin.html as Z_signin.html

2. Edited Z_signin.html ( Hiding Language Selection fileds and so on )

3. Set Z_signin.html with Signon Page on Look and Feel tab for Web Profile Configuration.

4. Reboot web server and application server with clearing cache.

It seemed to work OK first... but it behaved unstable.