I just purchase a Lennox Legacy c260 insert. I am having my brother in laws install it. They are having problems with the insulating blanket install. The directions seem to be vague. Anyone out there have any experience installing a C260? My brother in law also says that I do not need any attachment that would allow the exhaust to flow into the chimney. He said that the draft would pull the smoke out. Maybe I should get a professional to install the insert?