[Theme: Twenty Eleven] Showcase Featured Slider in Header

Hi there

I’ve successfully replaced the standard header image with the featured post slider from the Showcase page on my home page.

To do this, I’ve just (in a child theme) amended header.php as follows

if (is_home()) { [pasted in the featured code from showcase.php ] }
else { [existing code, so the default header images display on other page ] }

I’ve tidied up a couple of CSS glitches and have got the JS working, but I have hit one stumbling block: global $feature_class in content-featured.php doesn’t seem to work when called from my child theme’s header.php. As such, what should look like this:

<article id="post-29" class="post-29 post type-post status-publish format-standard hentry category-environment feature-image large">

Looks like this:

<article id="post-29" class="post-29 post type-post status-publish format-standard hentry category-environment">

That is, it doesn’t seem to be populating the feature class correctly. If I edit the HTML using Firebug to include the class, the correct CSS is applied and it works beautifully.

Could anyone offer a tip on how to get the feature class to define properly?