I have my fireplace set where I want it in my new addition. Right between two windows. The flue pipe straight up will just catch a truss. I checked at the local fireplace shop today and they have a couple 30° elbows for $125..My flue is the air cooled pipe. Can any of you tell me just how far two 30° elbows will shift the pipe over? He also has two 15° elbows. How much will they shift the flue pipe?