Be careful with fiberfrax 970 on the cabin side. The fibers are glued together with an organic binder. When exposed to flame, the binder outgasses. The outgas is both flammable and a smoke source.I have gone back to just putting a layer of Fiberfrax and another layer of plywood on the pilots side of the firewall.
Again, insulate firewalls on the engine side. The best cabin side is bare stainless, not even painted.