[TYPO3-ttnews] extend tx_news TCA not possible?

[Gerhard Mehsel]

Hello,

I hope my question is enough tx_news related. I want to extend the TCA 
of tx_news_domain_model_file. Is it possible?
In ext_tables.php of my own extension:

// -----------------------------
$tempColumns = array (
'tx_myext_news_preview_image' => array (
	'exclude' => 0,
	'label' => 'Teaser Picture',
	'config' => Array (
		'type' => 'group',
		'internal_type' => 'file',
		'uploadfolder' => 'uploads/tx_news',
		'show_thumbs' => 1,
		'size' => 1,
		'allowed' => 'jg,png',
		'disallowed' => '',
		'minitems' => 0,
		'maxitems' => 1,
	)
)
);

t3lib_div::loadTCA('tx_news_domain_model_file');
t3lib_extMgm::addTCAcolumns('tx_news_domain_model_file',
	$tempColumns, 1);
t3lib_extMgm::addToAllTCAtypes('tx_news_domain_model_file',
	'tx_myext_news_preview_image', '', 'after:title');

// -----------------------------

If I just change 'tx_news_domain_model_file' to 'pages' my pages TCA 
gets extended like it should.

What am I doing wrong?

Best reagrds,
Gerd