if you ditch the air cooled hoods on the other hand.. then you better make damn sure that your AC is a monster, and that you have adequate air circulation in those closed tents, especially canopy level.
if the air being pulled through your hoods is coming from outside, you wouldn't have to worry about filtering it.. but like someone said, the air temps will be an issue.
if you pull AC air direct from the unit and run it through your lights then you might have a problem with condensation in your hoods, which might eventually turn your garage into a bonfire.
if you exhaust the tents into each other..im not sure what would happen but it'll probably be hot as fuk.
if you're pushing AC through a split into both tents at equal pressure, that is probably the best, but without pulling filtered air from inside the tents, through your hoods, and exhausting it outside.. i cant see how you will be able to maintain 70-80 F. it's not the most efficient of setups, but its what I do. I have a 10,000 BTU portable AC that is linked with my lamp exhaust duct, it pushes cold air into one side of the room, while I have my carbon filter pulling air at the opposite end of the room.
i want to run vertical 600's and stop fukin around with the hoods, but its hot here - i just cant see any way around it. water chilled hoods are seriously inefficient, a 1/4 HP chiller only chills 2 600's, and not well I might add, at the price of another 457watts.. or something like that.
Why are you so set on makin it completely sealed? if you dont mind me askin..