I am planning on starting the framing on my Quadrafire 7100 today. Looks like it says in one place in the mantel that non combustible material needs to be used above fireplace to the ceiling.Then it refers in another spot 2x4 framing. I was planning on using wood 2x4 with concrete board covering everything. Is this ok or do I need to build it with something else? You guys got any pictures of yours when you constructed yours? Looking for some ideas on how to do the frond extension in front of the doors. Planning on putting up cultured stone when done.