Is my chimney too short for a 5.5" liner?

For those interested in pics, I have some of my chimney here:
http://www.hearth.com/talk/threads/feedback-on-c450-insert-install.99803/

I was up on the roof and measured my flue before I get a SS liner for the installation of a Jotul C450 insert. It is tight - probably 7x11. The stove has a 6" connection. My chimney is 14'8" from the top of chimney to bottom of fire place. The stove is 22" tall, so the effective height would be around 12'10". I'm worried that the 6" liner won't fit so I have two options - ovalized 6" or 5.5". Can anyone comment on if I can get away with a 5.5"? Can I make the 6" work?

Any input is greatly appreciated!

Tough call. They do make a smooth inner wall 5.5" chimney liner. That would increase draft some. If your flue is a true 7" inside you could use a 5.5" liner and 1/2" insulation giving you total diameter of 6.75". That would be tight but doable. If you have any doubts about that use the 1/4" insulation.

I think the better of the 2 options here is keeping the liner round. My vote is for the 5.5"

Knock out the flue tiles and you will have lots of room to drop an insulated 6. The more room you give yourself the less you will struggle installing the liner.

Knocking out tiles if professionally done should run about $300 and should take 1 to 2 hours.