Finally broke down and purchased the Harman Insert. Connecting it to an existing 4" flex liner. From the dealer and researching this forum, I have noted most insert the flex INTO the stove stub, silicone and secure with screws. I personally feel the flex should go over the sub eliminating any potential leak. The manual states The unit comes standard with a 4” pipe stub. • Part #1-00-574034 is for use with 4” PL vent starter pipe and 4” stainless steel flex pipe (Part #1-00-574034). Is there any specific adapter to couple the stub to flex or even if I had to place a rigid pipe adapter on the stub and add a short pipe to flex adapter?