[TYPO3-english] code after closing html tag

[Roman]

I need to place code for a page grading module 
(http://www.opinionlab.com/dialogcentral/) after the closing html tag. 
Does somebody have experiences in doing that? I didn't find any 
possibility to achieve it through TS. Does it need to be realized 
through an extension by adding a hook function to 
TYPO3_CONF_VARS['SC_OPTIONS']['tslib/class.tslib_fe.php']['contentPostProc-cached']?

Thanks for any hint, Roman