We bought a king bedroom set at a sale(our room looks very small now).  Now we are looking for a new mattress.  My wife would take the softest thing ever made, and those just absolutely kill my back.  Anybody ever to two TwinXL's and put together?  I'm thinking it would be O.K., but not liking the idea of a big hole or a step in the middle of the bed.  Right now I sleep on a bare quilted mattress, and she has a double layer of memory foam on her side. 

Thanks.