I would put some sort of reflective tape on the top surface to try and direct the heat down.
I have insulation tape on one side already, the side with the tape gets so hot that it will burn your hand if you touch it.
I have made a box for the panel to sit in, I'm hoping the box will focus the heat down more and also make it a little more safe.
I started with a peace of 16mm melamine for the top (bottom in the photo), then cut a hole in some industrial grade foam for the panel to sit in (the foam only touches the sides of the panel, not any of the faces) and screwed it all together with some thin bits of wood.
Because of how hot the surface of the panel gets, I added some shade cloth in-between the foam and wood strips, so the snake wont get burnt.
I'm in the proses of testing it now.
This panel won't be used with any snakes, this is my mockup panel, made from what ever scrap I had laying around.
If this works then I will be remaking the whole thing, I will router the whole box out of timber, so the panel box will only be made from 2 peaces (front and back) and there will be no foam in it (I only used foam in my mockup panel because I needed something to fill that gap with).
If this mockup panel doesn't work properly, then I suppose I could try moving the heat cord closer to itself and maybe put a couple of holes in the polycarbonate.