Hey jleuze,
i use the Meteor template-tag to replace the original header-img in a child-version of Twenty Eleven, and remain still the "Thumbnail Option". There is no problems with "the Header position" in Safari and Firefox, but as usual there is problems with IE8 and the css-style :-( ... IE8 showes a "very Big margin" between the logo-text and the Slider IMG's. See this link to my webpage!
I also try this "hack" in the original version of Twenty Eleven and it's the same problem, so it's not my "child-version" who make the "position" problem with Sh.. IE.
I'll try to add some unique IE8 CCS-code to my Style-sheet, but without success. Maybe You got an idea? - Here is my "hack" from header.php:
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// Houston, we have a new header image!
echo get_the_post_thumbnail( $post->ID, 'post-thumbnail' );
else : ?>
<?php if ( function_exists( 'meteor_slideshow' ) ) { meteor_slideshow(); } ?>
<?php endif; // end check for featured image or standard header ?></a>
<?php endif; // end check for removed header image ?>
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Thanks for a nice Plugin ;-)
-madzzoni