If you search for (overdue, 7 days), you will see overdue tasks at the top and 7 days tasks at the bottom, but if you look for (7 days, overdue) - the overdue ones will be go to the bottom.
This is the only option to change the display, it's unfortunately, not possible to also change the order of the tasks displayed. but you're welcome to request such option in our Votebox: http://todoist.com/Vote/
Perfect! That solved it for me! Thanks!