My name is Daniel Neidig. I love grilling and anything that's deals with it. I just finished build my fire box vault smoker Titan Smokr
Well then, Dave would know. I used it to build mine but it's a vertical reverse flow. I would try going 8 inches between fb and CC with a diffuser plate to spread heat and smoke out.Daveomak said that the calculator I only good for sfb or rf smokers. However I did get about the same numbers you got I did 4in exaust was going to see what 6in figured this morning.