[Plugin: Multiple Post Thumbnails] Only allowed maximum of 2 extra thumbnails

I am using the following code to give me 4 extra featured images in my admin panel:

// enable multiple post thumbnails
if (class_exists('MultiPostThumbnails')) {
    $postThumbnailType = array('post', 'page', 'service', 'equipment');
    foreach($postThumbnailType as $type) {
        $thumb = new MultiPostThumbnails(array(
            'label' => 'Secondary Image',
            'id' => 'secondary-image',
            'post_type' => $type
            )
        );
    }
    foreach($postThumbnailType as $type) {
        $thumb = new MultiPostThumbnails(array(
            'label' => 'Third Image',
            'id' => 'third-image',
            'post_type' => $type
            )
        );
    }
    foreach($postThumbnailType as $type) {
        $thumb = new MultiPostThumbnails(array(
            'label' => 'Fourth Image',
            'id' => 'fourth-image',
            'post_type' => $type
            )
        );
    }
    foreach($postThumbnailType as $type) {
        $thumb = new MultiPostThumbnails(array(
            'label' => 'Fifth Image',
            'id' => 'fifth-image',
            'post_type' => $type
            )
        );
    }
}

However I do not get 4 extra image fields, only two. It gives me the first and last fields; ‘Secondary Image’ and ‘Fifth Image’.

If I remove ‘Fifth Image’ then I am given ‘Secondary Image’ and ‘Fourth Image’.

Does anybody know what I am doing wrong?

http://ww.wp.xz.cn/extend/plugins/multiple-post-thumbnails/