1. you should be fine with a passive intake (holes) and see if you can get a little oscillating fan in the main grow area? if you can manage to put an oscialler inside on top of a lot of passive intake holes, that'll do

2. i'd guess that computer fans aren't gonna cut it for exhaust. you're going to need to move a lot of air out of there to cool that hps, and your plants will thank you with less humidity and more co2



you seem like you know what you're doing and you'll be fine. you'll have to adjust as you go just like anyone else, but i think you've got a good plan; just keep track of temp. PH, and humidity if you can; take it easy and you'll be fine; you'll always have to adapt