My local hearth store has been hopelessly unhelpful on this one. Pictured below is where my chimney enters above my hearth. The interior of the opening is 9 7/8". I have 8" double-wall pipe to run from the top of my stove, straight to the chimney. How to go adapt from the 8" double-wall to the 10" chimney? I can't find a manufacturer name anywhere on the chimney, even on the outside.