I run 11" belly heat for the hot side and 3" belly heat for the cool side. The only back heat I have is a 4x2ft hatchling rack that holds 6qt. sterilites. I have stripts of 3" flexwatt running down the back of the rack behind each stack of tubs. I myself prefer the belly heat. But it works out a lot better with the hatchling tubs because they are stacked 2 high on each shelf. I don't have any health problems with any of my snakes. They all eat fine too. I still have oil filled heaters from walmart that keep the rooms 75 degress. They are controlled by johnson therms.