The single-POSTTYPE.php option also works in child themes whereas the plugin only finds the file if it’s in the main theme directory.
You should use locate_template() instead of TEMPLATEPATH to make it available to child themes.
Not the tidiest of code, but it works:
$testing = locate_template(array($wp->query_vars[“post_type”] . ‘.php’));
if ( $testing <> “” ) {
$cptdt_template = $testing;
}else{
$testing = locate_template(array(‘t_’ . $wp->query_vars[“post_type”] . ‘.php’));
if ( $testing <> “” )
$cptdt_template = $testing;
}