I just purchased a new NC30 for my house to replace the old smoke dragon I had. The old stove was installed by my contractor and had an 8 inch flue collar on the stove. The pipe was installed on the outside of the collar. I see with the Englander it says that the stove pipe must be installed on the INSIDE of the collar. Where has everyone purchased their pipe for the englander? Secondly, my pipe has a damper built in. Should I get a new pipe without a damper or is it ok to have on there?