I'm getting ready to install a very heavy duty fireplace insert into a fireplace in a 219 year old colonial house here in Maine and because the brick in the chimney was so poorly laid that it can't be cleaned or trusted i had to install a 6 inch liner which is all i could fit down in the chimney. My question is this: I Need to adapt a 8 inch cast iron collector assembly that sits in slots on the top back of the stove to the 6 inch SS liner. I Found a heavy gauge steel black plate adapter/reducer on Amazon but am concerned about moisture/rust damage in the future and am wondering if a selkirk insulated type SS adapter/reducer might work?