So if I have a space of 106 cubic feet. (my guess of 1 door length 7' long)
Will 2 PC fans keep up to a 600w hps?
I assume I would need 4-6 fans.

Are HDD fans more efficient than the cpu or case fans?
Could line the top corner of ceiling with HDD fans mounted to each other in a row.
I assume these are approx. 2x2" fans.
Even smaller venting may be easier for me to shove through the roofs bracing.

I am confused on what is best.