Chimney length

[mcgyverism]

If my chimney needs to be a 4" diameter pipe, about 27" long (Based on the calculator) Do I weld it directly flush with the top of the smoker, or should it be a few inches inside the smoker near the top food grate?

 

[jakesz28]

I think the chimney should go to the food grate. Also if that is the length from one of the calculations. That is the length outside of the cook chamber.