Hi, My daughter and her husband just got a house that 2200 sq ft and i'm trying to lined up inserts to chose for them. The house has very high cathedral ceilings and 3 bedrooms upstairs. I think it's close to 3000 sq ft with extra space . The opening is huge in double sided masonry fireplace and can accommodate anything . 8 inch flue is not a problem, Straight run. If it was me , i would put BK freestanding King and be done. They want insert, of course . I have Travis large flush hybrid at my house and they want the same. I like the unite but would try to see something else in action. Looking for advice on biggest cat insert. might be 8 inch.