ok i have an older fisher, planning on installing with a direct vent with block off plate (planning on doing a full ss flex liner when finances are there). does anyone have suggestions on if i should use the brown death insulation above the block off plate, i'm kinda worried about the creosote landing on the top. as it is now i have to fabricate a hub for the top of my insert to pipe it up to the chimney, it has a 7.5" hole that's flat across the top so im probably going to use a 8" sch 10 pipe and cut and shrink it but i'm thinking about tapering it to 6" (is this a bad idea?) so the liner is cheaper. any help is greatly appreciated