Has anybody had any issues with the unibody shell on the 13" MBA flexing/warping? I have just sold my 13" as carrying it everyday made me paranoid that with it being so thin/flexy it would eventually cause warping damage to its shell. I have decided on the 11" instead, I tried bending a 13" and an 11" at my local Mac reseller and the 11" seemed rather rigid but the 13" definitely had some flex in it. Interested in hearing everyones thoughts.