This thread has some good analysis regarding car ports and SPL:so no increase in SPL/low extension?
I took out one and that solved the flapping/chuffing noise they caused, and i got higher SPL & lower extension.
I'd consider putting some of the flaps back and seeing if that changes anything. don't want to big of a "port" or you can actually lose SPL
I have noticed, especially in pickups. The bass hits much harder with the front windows down. I'm curious if anyone knows why this happens? I have some thoughts but I don't have solid enough sound science knowledge to be confident in my ideas.
I think you're right that there may be a sweet spot. I may have seen a 1-2db drop on my SPL meter after removing that access panel.