How tall is your tent?
LxWxH=cu ft of space.
You generally want your cfm* pullin 3 times the amount of your cu ft. I've got 2 exhaust fans pulling hot air out of 192cu ft. And can still get a little warm if I don't monitor closely.
8'' would be ok, as for temps, it depends on the ambient temp flowing in. Might need an AC if it gets too hot in the room itself. Ballast and lamp are also going to be producing heat.