I did this with an extra template resolved. In this template, there is only the login module (copy of cb-login modul) the position of this modul i use is eg user9 (not use in reglulaer template). you also net the plugin
Template selector
in my mainpage i call the cb-login in a iframe with the custom template (eg login):
[code:1]
www.yoursite.com/index.php?template_selector=login[/code:1]
see on my mainpage:
www.knuddelesel.de
probably you need a little experiment:S
... sorry for my bad english