Grow tent + 2x 600w HPS Heat issues

I have a 240x120x200 Grow tent situated in my attic. It has two 7" exhaust vents and one 6" intake vent. Temperature in the attic is usually around 20-25C, however with just one of the lights on the temperature in the tent can reach 35c. I currently have a 4" carbon filter and vents tt100 inline aswell as intake. I realise these are probably insufficent but would increasing the size of the fans alone solve the problem especially with both lights on? The only ventilation in the attic is a 3" shower room extractor fan that leads to the front of the house, that i have hooked up to the intake fan, however this only seems to blow a small amount of air into the tent.

Any help would be greatly appreciated.

If it is any cooler outside, if if your running your lights at night, running duct to a outdoor vent could solve your problem, if not buying 2 cooltubes and running air in and hot air out of the tent directly with a inline fan could easily solve your problem, and running your carbon filter with your existing inline fan- then you could buy a fan controller and keep the temps exactly where you want.