Yes I did that cos our house gets quite chilly at night so have used insulating stuff on the back . They also have large pieces of cork that they use to build hide away etc. The only thing I worry about is the temp drops quite dramatically at night and the night bulb is too hot for all night use so using the heatmats helps maintain the overnight temp

What`s the wattage and type of bulb you use at night, if it`s too hot, why can`t you use a lower wattage, either infra-red or a ceramic heat lamp?