I’m here whenever partner, can’t always say I’ll have the answers though haha!
Personally I feel like there’s a point where moving more air doesn’t really help temps much. Not without a big change in intake air temp anyway.
I have oversized every single one of my fans and filters for that exact reason. Usually I run way under capacity and things are fine. The couple of times I’ve ran into issues I could increase my fan speed from like 50-75% and see a little difference, but it didn’t make a big difference going from 75%-100%. It wasn’t until I made some changes to intake air temp that I got results I needed. Then I was able to maintain even at lower fan speed. If that makes sense?
That being said, I always try to have a little more than I need. Especially with things like dimmers for lights and speed controllers for fans. There’s nothing that agitates me more than having to buy something twice lol.
What I’m wondering is if there’s a way to mix some cool outside air into your intake? It would have to be somewhat controlled obviously. But taking a glance at your setup, anyway you may be able to do something like that?