I've got an older stove with an 8" collar, and a masonary flue with an 8x12 liner. Probably be replacing the whole thing next year anyhow. But we always have had a tough time getting the thing going. The top down method is something I'll try as well. But They hooked the stove up to the thimble with 6" (reducer on stove collar and reducer on thimble). Would it make much a difference if I went 8" from the stove to the thimble and skipped the two reducers? Crappy pic is attached: