youll be fine, i dont even vent my 400 watt light in a 2x4 foot veg tent, AND passive air also works for me in my 9x9 2200watt flower room too, 5-600cfm out and passive in all the way. running a 1000watt light and 2x600's and a 8000btu portable ac unit.
dont overthink it man
and FYI my veg...