I have a standard 8x8 lined chimney with a 6" wall thimble mortared in. I want to line with a ss liner, but a 6" "T" isnt going to pass through my thimble correct? So should I use 5" or a 5.5" instead? That way it will be smaller in dia to pass through the thimble. The thimble has been built around so it needs to stay where it is if possible. My englander stove has a 6" outlet.........