You could try radiant heat panals but I heat all my Visions and other cages with Exoterra Heatwave pads. Thin, consistent, and very safe and nicely priced. I have used many for years and so have a lot of my friends and I have not heard of these pads burning out or causing fires. They slide nicely underneath or in between the Vision cages. I do not sitck them to the cage-I leave the paper backing on the pad and attach them to the cage with strips of aluminum foil tape along the edges of the pad.
I recommend getting the cage up off the carpet no matter what heating system you use. Go to Home Depot and get a thick sheet of plywood cut slightly larger than your cage and some cinder blocks and you have a stand that will work well for you. Hope this helps-Bill.