running a cord under the mattress would seem like a good idea but according to an old electrician friend of mine it not a good idea. he told me many years ago that the cord must have a way to cool it self, and running a cord under some thing such as your mattress will keep that cord from staying cool and may over heat. are you willing to take that chance. my self I would run the cord around the top edge of the bed base and put in those little plastic cord holders. it would be able to breath and be up off the floor so you can't trip on it
