Will a wider ridge vent slot provide more Net Free Area through the vent?

Cutting a wider slot will not increase the Net Free Area of the ridge vent.

Cutting a wider slot will not increase the Net Free Area of the ridge vent because the Net Free Area is specific to the vent openings in the vent itself. For example, ShingleVent II ridge vent has 18 square inches of Net Free Area per linear foot. Even if the slot were wider than recommended the airflow through the wider slot must still go through the actual ridge vent. The ridge vent will not allow more than 18 square inches of Net Free Area per linear foot. Note: If the slot for a ridge vent is cut too wide there is potential for weather infiltration because the slot may be too close to the louver openings on the ridge vent.