I have a Hearthstone w/top flue collar. It has a big baffle inside, so if you sweep the flue the creosote falls behind the baffle. Removing it to clean every time is kinda of a pain in the arse. I am moving the stove from my shop to the basement of my log house that is still under construction and installing 8" doublewall Duravent. Initially I planned on having the flue terminate behind the stove, then 90 degree-ing up and over to it. I was playing around with it today and stuck the "T" right on to the flue collar. Any reason not to do this? Clean out would be easy, just stuff a rag in the bottom of the "T", sweep, vacuum & pull out the rag. Also it eliminates that 90, which I really don't like in my system.