Cab. Set up & Ventilation Questions

In a 3'L x 1.5'D x 6'H cab, the measured volume should be ~27cubic ft.

For 3 to 5 room exchanges per minute, anywhere between 100-150CFMs should be fine. Note, I would like to have a one fan ventilation system if possible. Cab would have passive air intake through four 0.5"x0.5" holes in the top corners plus door cracks and hinges are not airtight.

How many CFMs would you tack onto the required amount (150CFM) when using an air cooled reflector w/ glass window enclosure, using lets say 400W HPS (or any size, 400, 600, 1000W)?

Is pulling the grow space air through the reflector's 4" 'Air-In' duct efficient enough when the lamps are either on or off?

What are the advantages of an inline fan over a squirrel cage blower? A 4" Inline (172CFM) votex fan is the same price as a 600CFM 6" blower fan which could be dialed down.
http://www.bustan.ca/product_detail....1&SID=13&PID=8
http://www.bustan.ca/product_detail....SID=13&PID=887

Lastly, I want to know some opinions about some possible cab. set ups, or questions if they're not clear in the drawing.

Thanks!