Using the other UTH with a second thermostat is one way of doing it. What type of thermostat are you using? I have had problems creating gradient heat accross a tank using an On / Off type for some reason, but if you do use the second UTH on the cool side set at around 80 - 82 an On/Off type should be fine as long as it is set to 1 degree variance. What type and size of enclosure are you using? Also are both hides the same type? The BP may be choosing the cool side as the hide is better suited for it.