Does′t work with BuddyPress

I found this code in parorrey.com, but this code is to set a front end avatar uploading, and I only need buddypress use the core avatars thru simple local avatars plugin.

So, I only use the add_filter that replace the image source.

add_filter('bp_core_fetch_avatar', 'local_bp_insert_avatar', 3, 5);
function local_bp_insert_avatar($avatar = '', $params, $id) {

    if(!is_numeric($id) || strpos($avatar, 'gravatar') === false) return $avatar;

    $pic = get_user_meta($id, 'simple_local_avatar', true);

   if (!$pic['full'] || $pic['full'] == '') return $avatar;

    $avatar = preg_replace('/src=("|\').*?("|\')/i', 'src=\'' . $pic['full'] . '\'', $avatar);

    return $avatar;

}

What I can′t find a way to use the thumbnail size of the avatar image file and not the original size.