Advice on How much ventilation ?????

What up guys,

I really could use some advice on my cabinet. here is a diagram of the unfinished cab. I have not cut any holes yet as I am not sure how big my fans need to be. . I need 1 fan to pull thru a 4" duct on a 400w hps and 1 more fan big enough to pull thru a carbon scrubber and vent out of cab. stealth is a must so the scrubber must be big enough to work but not allow for to much aspiration of plants. I can go passive or not on intake.

Lets me know what you guys think. I have lurked these threads for awhile now and have started my own stealth cab.

P.S. If i left out any important info please let me know.

i got my 4" fan & filter from them. good deal $99 for fan,$139 for both. you want to achieve a "negative pressure" in your room or tent, so go passive intake or 4" for intake and 6" for exhaust.

how many cfm's ? I have a small blower approx 100 cfm would that be enough to cool the cool tube?

You've only got 37.5 cubic feet in your flowering chamber. You want to exchange the air at least once every 5 minutes, so your 100cfm fan will be fine.