How did it go? Did you ever get rid of the 41Hz peak? I have a 43Hz peak in my 4.1x5.0x2.38 meter listening room. 4.1m to the rear wall. I have a spare sealed Eminence Lab12 sub. It sucks at anything above 80Hz, so it was replced by a pair of Seas Excel 10 inch woofers but as good as they are above 100Hz, below 100Hz looks similar to what you got. I could out the LAB12 in the rear of the room and see what happens. If it cancels out the peaks.