So I just opened up the wall of my old ZC fireplace as I am planning on turning the chase into an alcove for the new wood stove. I am pretty sure I am going with a lopi endeavor due to the close clearance ability. When i tore open the wall i have a span of 54" between the studs where 50" is required. I plan on removing the paper faced fiberglass insulation and replacing it with roxul and then installing 1/2" durorock and then either tile or cultured stone on the durorock. This would technically bring my clearance to under 50" (with the cultured stone 49") but someone please correct me if i am wrong that the clearance to combustibles would remain 54" as the 2x4 is the first combustible encountered? I am still nervous about being so close to the minimum clearance, but also feel that the durorock and will provide me with some R value before any heat gets to the studs. Would anyone be concerned with this installation. I could always go to a protected surface but dont want to complicate things and add cost to the install for no reason, I also thought about painting the entire inside of the chase with fire retardant paint before i put the new insulation and durorock in. Any thoughts/ suggestions/ ideas are all welcome