Heh, I am not to knowledgeable when it comes to airflow. I am thinking if you are FORCING air through with your lower intake fan and the upper intake fan is trying to suck what you are forcing through, causing to much? Perhaps eliminating the lower intake fan and just having the upper would be better than what is going on now? And if you have to wait for a larger intake fan, perhaps getting a y-connector and connecting both existing 160cfm fans to the upper ducting would also help? And if your temps INSIDE the room were lower than cooler air would be pulled through the ducting of the LOWER port (WITHOUT AN INTAKE FAN) thus cooling your tent. Portable AC? And rid of the portable heater! I like my temps to be mid 60's when my lights are off, if possible. Tho summer time is a-coming!
Oh gosh, I cannot remember names, yet, though I think it was bamagrow who referenced the radiant heat from your bulb.
Edit: I tried to find the formula for figuring out what size fan should be had with dimension of growing space. Ahhhh! I'll search some more!