this is what i got rigged up for my 2x4 double chamber 2 level tent ,running a air cooled 600 for flower and a air cooled 250 in the veg chamber ,i built a custom fitting out of heavy cardboard and ran 2 x 4in ducting to each chamber and also set my ac unit on a couple pieces of 2x3 leaving me a gap under the ac to vent from ,youll see i also built a fitting and exhaust out of that, temp stays under 28 and on the hottest days it might hit 29 but i have never seen bugs under 30 so it works for me !