Help with my flower box- Ventilation and C02 help

Hello all
well, ive been reading on here for a while and finally signed up

anyways, i currently have a box i built for flowering that is 42" deep- 74" long- 50" tall

i have 2 600w HPS that are air cooled with 6" ducting with 2 duct boosting fans

also have 2 duct boosing fans in side of box just to ventilate the box to keep temps down

with all fans on- temps are steady at 82* lights on and 70 lights off

Now i am having an issue with wanting to add c02 and i feel its an issue with the 2 fans venting out the box as the c02 would simply leave the box also









there are a few various pics of the box to show the ventilation and how the fans are on the side, with a large door that is hinged and folds up from the front

SOOOO MY QUESTION

how can i lower temps efficiently and then distribute c02

was planning on getting a 50lb tank and a hydro innovations controller
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260492561888&viewitem=&sspagename=STRK:MEWAX:IT

also thinking maybe my duct boosting fans are the reason the temps are high but fine with all fans running as long as lights are on

so maybe i was thinking hydro innovations heat shield for the enclosure and then upgrading fans to better pump hot air out


anyways, just looking for some greatly appreciated input on on how to keep the enclosure cooler and allow use of c02

if i dont run the 2 fans for pure ventilation, temps reach 92-93*