What type of rack do you have? An open side rack is designed to use the heat of the room to help regulate temps...in essence what the large breeders do is heat the room (then the flexwatt just provides a hot spot). If you have one of these racks it is very difficult to get a good temp gradient without regulating the room temp...the option is putting flex on both the hot and cool sides and have 2 thermostats to regulate the temps.