In reply to getandy:
I doubt you will have problems, but if you are still worried about your mat, you can have a contingency plan.
Unless it is brand new, I think you will be surprised how much you can reduce the length of the mat.
Get a couple of heavy duty straps and crank them up, the mat should fold to a point that is within the dimensions.
I would take the straps with you, but only use them if you are challenged as the mat does take a while to restore its shape if they remain on for any length of time.
I have a 25cm mat similar to the DMM but only a relatively small thickness of the mat is the stiff type of foam.
Failing that and more of a pain, but you can take out the foam and it will bend much more easily.
Many companies do have a habit of being very good for years and years then suddenly one day the rules start to be enforced more strictly.