I have the belkin mini portfolio for the x50 but havent used it because it looks like the velcro tab would put pressure or rub on the unit. Then I looked at the others and it looks like the cards would rub even more. Im assuming this must not be a problem since no ones complained about it but my engineering mind just cant see how it wouldnt damage the front or the touchscreen. Heres pics for reference.
This is the one I have now
This is the one I thought I ordered
Which looks to be an even worse idea