I have an existing heatilator fireplace and this is the 8" chimney for it. I've used this chimney to vent an old Scandia wood stove with a 6" flue for 5 or so years. I know it's not ideal for draw to go from a 6 to 8" chimney, but does this look like it's safe? I've used it for about 5 years. Have I just been lucky or does this look reasonably safe based on these two photos? I feel confident in my connections below. It feels like thick enough material and it's double walled. Any advice is much appreciated