I have a Lopi Model X insert that has a flat top around the exhaust opening. There is no collar sticking up in which to attach a pipe. This stove has a secondary burn tube and seems to be made almost like the new Lopi model, except for the flat top. I'm fairly certain this was made in the late 80's into the early 90's given the secondary burn tube. But, I think it was made when people just set inserts into their fireplace without worrying about connecting it to anything. My thought is to have someone weld a ring around the top but I'm told that you can't weld onto cast iron. Is that true? I'm not certain whether the stove is cast-iron or just steel. Another issue is that damper you see in the photo. It protrudes into the exhaust opening on-top. My thought is to have a ring welded onto the top that has a little notch in it to accommodate that damper mechanism. Any thoughts are appreciated. It's a well made insert and I'm looking forward to making it like new again.