I have 2 small helix radiant heat panels that I use on 2 of my enclosures.
I had nothing but trouble trying to keep the snakes off of them.
My balls LOVE to climb. They just aren't very good at staying up there.
The description for the panels said the surface never reaches temperatures high enough to burn an animal however even with them connected to the thermostat the very center still got hotter then I was comfortable with and the snakes LOVE climbing on them. The hottest part being the bottom center when mounted to the roof of the cage.
The panels I have, have a lip around the outside thats roughly about a cm wide and both snakes would climb up and lay on the lip of the panels every single night and at some point during the night part of their body would slip off and the weight of their tail would drag them the rest of the way off and they would fall.
The enclosure is about 2 foot tall and they would just stand on their tippytails so they could reach them to climb up.
So there was the problem of them falling from 2 foot up to the bottom or on top of whatever branch/log/water bowl they might be over. I originally had them inside the cage connected to the top using the L brackets and pegs they came with. With that setup there was a gap between the top of the panel and the top of the cage. First thing they did was climb on top of the panels. The top of the panel wasn't as hot as the bottom but there was the concern that they may end up pulling the panels down on top of themselves. So I drilled holes in the corners and bolted them up flat and secure as per directions that came with them.
But that left a small gap between the bolts and the corners of the panels...which was just enough for a head and neck to fit through...and reminded me of a snake gallows waiting for them to stick there head in and then fall.
The thought of finding a snake hanging by its neck was enough to make me say screw it and remove them completely from the inside and mount them to the back of the cage so that the heat would come through the metal screen back.
As much as I like the idea of heat panels It just turned out to be a bad idea for my enclosure. I could have taken a piece of wood and made a frame to fit in the lip but it was easier to just take them out and mount them on the backside of the cage. I also figure that would be more energy efficient then having the heat go straight down but I don't know for sure.
If you use them make sure you plan out the exact placement of them, how you are going to attach them to the cage and how you are going to secure the wire so that they are not able to get to it to use it as a swing as well.
I had purchased the heat panels before building the cage and had them on top of the tank like a ceramic heat lamp would be used which worked fine but the design for the cage I built changed a few times during construction so everything else had to evolve as I went too.