Sagging and ridges

I really wish we'd read these reviews before buying a Cloud Nine Gel mattress! I must say that I'm very disappointed with the hollows and the ridge in the middle. I'm going to throw my expensive **** mattress away. Cloud Nine did come to measure the sagging but says it's within "normal limits". Also blamed us for using an electric blanket! The sore backs and pain aren't worth it. Do yourself a favour and just NEVER buy Cloud Nine!