I need to replace the stove pipe on my keystoker. It started as an easy job, until a rusted out fabricated adapter fell out of the chimney. Now I have 7" pipe (from an increaser) that needs to fit into a 9 1/2" chimney damper/flue. I read on another question that I would need to fabricate an adapter. Any ideas what I should fabricate it from to get to 9 1/2" in diameter?