Venting for 2 - 2x4 tents

Would an 8 inch fan be enough for 2 - 2x4 tents? Both are using Spider Farmer SF4000's. I'm worried about noise but I can deal with it to bring temps down from the mid 80's.

Yes. I use an 8" to vent a 4.5'x5'x8' space. The 8" has enough power to pull a negative vacuum on the room.

Do the math on total cubic feet of the tents. Plug that into one the many online HVAC calculators. Add at least 200cfm to the total.

Air takes the path of least resistance, one tent will more than likely be effected more than the other...similar to how a house with central air or heating always has one room that is hotter or colder than the rest of the place.

What's wrong with mid 80s for plants under LED?