Gerbil, this is probably the first time I've disagreed with your advice.(posted 9670 days ago)I highly recommend NOT converting from a stovepipe directly into a chimney. While I have never done this personally, I have heard from many reliable sources that this will cause lots of creosote in the chimney, because the chimney will cool off the smoke so much. At some point all the creosot can cause the hottest flue fire ever.
I'd recommend getting your local wood heating store to confirm this; I think they will tell you to put the stovepipe all the way from the heater to above the chimney