Painfully familiar. I chased cables for months before treating first reflections and the center image finally locked. For people starting small: would you prioritize side-wall panels or a pair of thick corner traps first in a typical living-room Hi-Fi setup?

The flow-resistivity point clicked for me — I almost packed dense board into a deep corner trap. For the air-gap tip: are you usually matching gap ≈ panel depth on walls, or going thicker in corners where you can afford the footprint?

This matches what I ran into after adding a second sub. Boosting the null just made the amp work harder and the seat still felt empty. Curious how you're placing the second/third sub in smaller rooms — opposing walls only, or have you had luck with a nearfield sub at the MLP?