Good Afternoon Everyone, I actually only have a couple of questions. This is my very first time attempting to build a smoker from scratch. i have had some serious progress and i think it is coming out very well (full post on my build will be when im done and will include pics). i used "Feldon's BBQ Pit/Smoker Build Calculator" for the dimensions of my design. I am now down to the part where i need to attach a chimney stock on the top of the fire box. The calculator suggests a total chimney volume of 190.40 cubic inches. The calculator allows you to put in a recommended pipe diameter and then tells you what the length needs to be. I don't want a ridiculously long chimney coming out of the top of my smoker so i chose 4.5 inches as the interior diameter of the chimney putting it at about 12" long. I'm ok with that length but i can't for the life of me find a tube that is 4.5" interior diameter with out the walls of the pipe being over 1/4" thick. I thought because of this i might as well make the chimney square shaped but i am really shitty with math. What would be the proper dimensions for the chimney if i wanted it to be square or a rectangle (190.40 cubic inches)? or can anyone tell me if there is a place that will make a custom chimney for me that won't be unreasonable in price? I greatly appreciate you time on this. V/R Jason.