Hi I'm new here but read many of the post. Bought house with a 70s heatilator with a 9'' I'd 14' od metalbestos pipe going up though the roof with flashing and cap. I'm scraping the heatilator framing and all. Putting in a country comfort cc1000 free standing air tight stove that is U.L listed. Question is can leave a portion of the old metalbestos I.e from the inside ceiling thru the roof. Thought was to use a 6'' to 9'' reducer near the ceiling running black single pipe wall down to the stove. Or to just run the 6 inch thru the old metalbesto pipe.