I used the soldering iron again to make a hole on top of the box (where the heat is from the lights..duh) for my fan to blow through. A cd was the perfect thing to trace as it was exactly the diameter of the computer fan i will be using.
Next I used the soldering iron to make a hole for the passive intake.

The active outtake must be larger than the passive intake or you wil lnot have any 'negative pressure' (airflow) through the box.

my ratio is about 2 or 3 to 1.

4 inch fan with 2 inch passive intake