I have 4 of these 18'x28'ish brick panels that came out of a natural gas pool water heater. They seem a lot like fire brick material to me, they seemed to have served the same purpose as our firebrick. So I'm trying to find a use for em. Any reason not to set them on the back and sides and top of my insert? Hold a little more heat in maybe? I don't know just a crazy thought.