It's my belief that passive ventilation is always the best solution. A rule of thumb is passive ventilation requires 2 times the area of your extraction fan.
Whatever dimension you have to cut to fit your fan (which should be on top of your cab, as heat rises) you must cut 2 of the same size...
Why would you want to go thru the hassle of wiring 3 when a single 150 hps security light would be perfect for your footprint?
Don't believe the hype that similar cfl wattage will produce less heat.
Your dimensions would just right for a vertical (extend the bulb and hang it directly from...