Something consider about the venting:
The convective effect of "air draw" means that the size of the intake - at or near the bottom of the device - is more important than the exhaust vent ( at or near top )
The size of the intake should be equal to or smaller than the exhaust, and having them both adjustable is best. But for just smoking - just a hole that is 3/8'' - 1/2'' in diameter is more than enough. The exhaust being adjustable is more important to controlling airflow thru the chamber, and thus - affecting the temperature, velocity of air thru the chamber ("dwell time" of the smoke) and...something we do not often recognize - the moisture content of the finished product.
i.e. - a really good cold smoke chamber design - is NOT a good jerky drying chamber. You would want much more thru-put of air, to assist with evaporation.
Conversely - for smoking/cold smoking cheese, fish, nuts, etc - you want only enough air thru the chamber to sustain low smolder of coals/pellets/wood chips.
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