Where to locate thermostat sensor

[lonewolf1253]

I just received a Boaphile snake cage which is 5 feet long and 2 feet wide. 17.5 inches high. They come in two sections which are bolted together to make that size. The left side has a radiant heat panel on top and an under tank heater on the bottom. The right side is the cool side. I'm debating where to locate the sensor?
I've seen some vids on you tube where they place the sensor under the UTH but that makes no sense to me with a radiant heat panel. Should I drill a hole in the cage and locate it somewhere in the middle? Or on the wall in the warm end? Any advice would be appreciated.