How tall is your tank. I am wondering if the added height of the tanks I used may have an impact. My blueys cages are 2ft tall and the one I am building for my Tegu is 3ft tall. When I was messing around with the 2ft tall cages I had hooked up some thermocouples to a temp sensor/recorder, monitored with an IR camera and noticed that anything past about 10 inches away from the RHP was not affected.