![welcome :welcome:](./images/smilies/welcome.gif)
First off yes your 4'' pipe coming from the firebox is way too small. There is a pit calculator on the main page of this site, if you run your dimensions through it you will get a formula for your build. I would start off by entering my cook chamber dimensions and build from there. It will give you a size for your fire box, throat opening from FB to CC , air intakes on FB, stack size and length. The guys on here use a baffle plate instead of a pipe, if you look at my build " The Ugly Stick I have some pics for you to get an idea of what I'm talking about and you're always welcome to ask more questions.