Silverlight Printing Issue

I try to describe the problem. In the example i'm using the Microsoft XPS printer but in reality i've this problem with Printers which print Cards and Label and printer needles.

First i go in ControlPanel -> Printers -> and i set a custom setting  for the XPS Printer:

After that when i Print from my Silverlight Application i have this scenario :

As you can see the paper size is not the same as i setted from Control Panel.
But if i set the XPS printer as Default printer i don't have this issue.

Thanks