ya I was thinking about going to 6" for clearance at ceiling.I didn't mention pipe size. Is this 6" or 8" chimney - ID? If 8", maybe now is the time to replace with 6" chimney pipe? That will bring clearances into line.
Re: pyrolysis. Wood gets drier over time and with continued exposure to heat it's ignition temperature drops. I can't say this will ever be safe, even with a new stove. And then what happens with the first space out leaving the air open or with the first chimney fire? Hopefully this won't happen, but it's why these tested safety margins are in place.
tn20 is 6", just was not planning on 3-400 bucks for pipeing, thanks again