I decided to put the active vent inside the combing  box.  Using the large circle saw you need to be careful, a lot of torque transfered so be real gentle as you start the hole.
The vent fit in the combing box and its positioning helped me not have to make an opening directly expsed to the weather.  The intake is mounted on the stern, and by being on the transom could produce some negative pressure in the locker. 
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