Slide image in RSS feed

How can I use the image from the DCG metabox and use it in the wordpress rss feed as a featured image instead of the default featured image

I am using this code in the theme functions php file

//Function to add featured image in RSS feeds
function image_in_rss($content)
{
    // Global $post variable
    global $post;
    // Check if the post has a featured image
    if (has_post_thumbnail($post->ID))
    {
		$extra = "<p><b><a href='" . get_permalink() . "'>Full Story...</a></b></p>";
        $content = '' . $content . $extra;
    }
    return $content;
}
//Add the filter for RSS feeds Excerpt
add_filter('the_excerpt_rss', 'image_in_rss');
//Add the filter for RSS feed content
add_filter('the_content_feed', 'image_in_rss');

What do I need to change/add to make it work with DCG

https://ww.wp.xz.cn/plugins/dynamic-content-gallery-plugin/