Smoker for the Bavarian Forest

[SmokingForest]

Hello all,
I live in the Bavarian Forest and smoking is not that common in my area.
But on several trips through the States I discovered BBQ for myself and since I love cooking, grilling and welding I wanted
to built a smoker.
I have already read a lot of forum posts and guides.
The biggest question at the moment is how big does my firebox have to be?
I have access to a pipe with an inner diameter of 480mm (18.9").
The cooking chamber should be 1000mm (39.4") long.
Now it seems to me as if it is a question of faith whether the firebox should be 1/3 or 1/2 the size of the cooking chamber.
My smoker should be a standard offset smoker and not a reverse smoker.
What do you think about this ?

Kind regards,
Alex

 

[Gonna Smoke]

First I'd like to welcome you. Next, I like your ideas, but I'm no smoker builder. There will be plenty of folks who will offer you suggestions. Just be sure to post some pics along the way...

 

[SmokingForest]

Thank you very much.
Photos and a report should not be a problem.

As a supplement to the first post, I have to say that the available pipe is already designed for a ratio of around 1/3.
According to the Feldon calculator, 108%. There are many opinions on the size ratio, but this one convinced me.

So talking about firebox size? - SmokerBuilder.com