Hi,
Add this to you child theme's functions.php and modify to suit your needs.
add_filter('tc_global_layout', 'my_custom_layout' );
function my_custom_layout( $layout ) {
$my_layout_for_categories = array(
'r' => array ('content' => 'span6' , 'sidebar' => 'span6'),
'l' => array ('content' => 'span6' , 'sidebar' => 'span6'),
'b' => array ('content' => 'span6' , 'sidebar' => 'span3'),
'f' => array ('content' => 'span12' , 'sidebar' => false),
);
if ( is_category() ) {
$my_layout = $my_layout_for_categories;
}
//sets new values for content and sidebar (checks if there are new values to set first)
foreach ($layout as $key => $value) {
$layout[$key]['content'] = isset( $my_layout[$key]['content']) ? $my_layout[$key]['content'] : $layout[$key]['content'];
$layout[$key]['sidebar'] = isset( $my_layout[$key]['sidebar']) ? $my_layout[$key]['sidebar'] : $layout[$key]['sidebar'];
}
retu $layout;
}