Ok... so I need to make sure my current Tumi Alpha briefcase will accomodate my new W520 with the 15.6 inch screen.... Im not sure what size bag I have, can someone help me identify which exact model I have...? Im guessing I have a medium sized screen bag, and Im not sure that the W520 will fit... I may have to buy a new Tumi bag but would like to make sure before making the purchase. Thanks !!