In my case I have two 6" intakes for my flowering room, (14L x 7W x 12H) one intake has a 140mm fan coming from my veg room, (7L x 7W x 12H), the other is a passive intake from the opposite side of the flowering room, crawl space air that is very cool. Helps allot !
I still maintain negative pressure. I run a couple cool tubes and a massive 6" intake mountain air scrubber. The flower room air never gets hotter then 63-74 degrees. That's 2x1000w & sometimes a 600w added in if needed. The veg room has only a boosted 400w and some HO T3s. Usually it's like this for most of the year except you know when months ... Lol then I have to tweak some stuff.