You want to set your radiant heat panel to one side to provide a gradient. With my rhp, I don’t need uth as well. For my temp probes, I have them about an inch to an inch and a half off the cage floor directly below the rhp. Basically as close to where the snake will be without risking it getting wet, even with substrate. Your thermostat will actually be set lower than your hot spot because the probe won’t be directly under the heat, but off to one side or behind. It takes a bit of tweaking, but I’ve never had issues once the thermostat was set.