I just had my chimney cleaned and inspected. I bought a used vermont casting winterwarm insert, and wanted to know do i still need to line the entire chimney with 8" ss flex tubing or can i just use the 5" piece that came with the stove. the top hole on the stove is oval this pipe piece is shaped oval and will fit thru my damper without breaking up anything in theflue? i'm just not sure what to do> any suggestions will be helpful. Thanks and Happy Holiday's to all