Is it ok to drive with the bed mat and no tailgate?

I doubt if it would ever fly out unless you somehow managed to break the sound barrier. That being said,for your peace of mind,and on the off-chance that anything that can go wrong will go wrong,tie a rope in an X pattern between your bed stake pockets and down to your bumper. If it were to fly up,the rope should hold it into the bed.

I,for one,appreciate your consideration for the welfare of other drivers.