That's a different looking mount than I had on my 2002 W22, but level sounds right to me. The bar will move up and down with the spring, so its not a big deal how it mounts as long as it moves freely and doesn't bump into something else in its travels.
Hopefully somebody with more recent experience will respond.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL