Thanks for explaining some more. The filter solution works with adding the class BUT the styles seamless / WP Metabox are being reset. If anyone’s going to use this code, make sure that you re-include seamless into $content[‘style’], else you get the WP metabox style.
I’ve contacted Elliot via Twitter. I’ll explain what i mean exactly and will update this topic when necessary.
Thanks for your help Hube!
