Hitzer 82 With 6" Chim.

I have a 6" ss insulated chim 21' tall from the T.
I'm wanting a furnace or stove with grates that I can burn wood 25% coal 75%of the time.
Hitzer 82 has a 7" collar, Dean says 6" should work 99% of the cases.
Does anyone have any experience with a 6" flue.

I have the predecessor to the 82, a75 the only difference I can see is the height of the firebrick other than that I think they are pretty much the same. In any event I reduced from the seven to a six & it works just fine.