Dryer vent stack extension mod....question? I keep meaning to ask this question when anytime this mod is discussed; but always seems I would be hijacking someone else's thread. Thought I would start my own. Perhaps I need to do a search and do more homework, but I don't understand what keeps most of the heat and smoke from wanting to travel under the grate and up the stack when you extend it down to the grate. Are we to assume here that the heat and smoke goes strait up when it enters the chamber and therefore has be forced back down by the extension. I haven't yet added this mod to my chargriller because I don't yet fully understand how it effects the airflow. Ejamakate me!