Bardis Sun Studios replaced all of their mattresses last summer with two sided ones. One side is s-o-f-t and the other h-a-r-d. If in doubt, turn it over..... But I can't offer verification, even after three weeks on one. My back is OK, and I have to admit that I could sleep on the floor of the Nut, or the beach, or MY bench opposite Thalassa. But Jen finds them very comfortable so I am posting this.
Beware though, in high season they are fully booked a year in advance. Their season ends early so plan ahead. Nobody is going to be in room 10 next July except Jen and me.
Phil