The back plate on the p6x58d premium is to thick

[widemouth]

The Q sheild on the P5X58D premium is to think and through the top three mother slightly out of alignemt 3mm from the center of the post where the screws go in. Do I really need the Q Sheild? My tower is a standard atx chasis that recently held my P5W DH Deluxe which is the same size as the P5X58D. I not sure buying a new case would solve that problem

 

[mosox]

You probably need to push it in harder. You can do without it though.

LE Check if the case isn't warped, push the back.

 

[Rusting In Peace]

Ah I see there is a difference between an IO shield and this Asus Q shield (no pins)

I'd do as mosox says but in my opinion it's far better to run a system "closed" so I'd persevere with it.