I hope Im posting this in the right place. Forgive me if Im not. Im building another custom pellet powered fridge smoker. I have a 6" diesel exhaust stack that im going to make my smoker stack out of. My question is, how long should it be? I know there is probably a science about it somewhere, but I can not seem to locate it. My inside box dimensions are roughly 50"tall x 22"wide x 16"deep. I found a calculator for stick burners, but nothing for pellet powered stuff. Any help is greatly appreciated!!! Thanks Ken