Imagine the brown panels as QRD, and Black as Absorption.
The Absorption Panels are:
beside each speaker are 12" thick, R19
Rear corners, 8.5" thick R19
Ceiling cloud (not shown) 2" OC703 with 6" R19 above that. Cover entire area between listening position and speakers.
Front left corner - 4" OC703 24" across corner with outward facing FRK
Front right corner 2" OC703 14" across corner (all the room their is with the door in the way) with 4-6" R19 behind also with outward facing FRK.
The QRD panels are:
single N7 throughout (12"Wx48"H) except flanking the listener where those are N17's (28"Wx24"H).
My "fixing" was changing the angles on some flat panels on side walls that redirect energy to the rear (not shown) to the left and right of listener.
I drive one channel at a time for ALL my tests.
As you can see, I did fix the 22.5ms peak fairly well.
Here is a better detailed ETC showing both channels only to 30ms
I have lots of info. Just tell me what is helpful and I will post it.