the smoker's exhaust is dee-you-double-N.
it took about 4 solid hours to burn it out then another hour to mount it. the mounts were done after the pipe was solid because with all that heat it did warp a little. so once it was cooled off the spring hooks were located and the mid-mount was handled.
everything clears and it's leak free.
PS: all of this was done about 2 months ago and i really miss my shop.