Suitability of Hybrid 4 for 18 stone man and 14 stone wife.

Suitability of type 4 (Tempur cloud option) for myself . 18 stone 5.9" with lower back pain,especially in bed !! Have spent a fortune on various mattresses without success. Latest purchase was a 2000 pocket sprung with a 50 mm memory foam pillow top from Highgrove (Allure). This makes my lower back problem far worse, rather than better. The most comfortable mattress I have tried was the Tempur Cloud. Your type 4 Hybrid would seem the nearest option. How would you rate it's suitability for myself