Keep in mind that center mounting skis really isn't the best for skiing switch. If you think about it, your leaning pretty far forward when your riding switch. This means that your center of gravity moves out past your toes. This is why you want to be running at least 2 cm back. This will help to equalize that effect and increase stability when riding backwards.
Additonally, most skis are getting away from symettrical sidecut just for that reason.