After searching a bit, I found the undamped base plate, it played together with subwoofer at deep bass tones, according to the picture, I only put dampers in the 4 round points in the middle and left of the picture, muffled wheel noise is an added bonus, I didn't do it all the way through the...
Small tip to remove resonance (barrel sound) from the trunk, remove the foam and subwoofer, and hit the bottom of the car with your knuckles, it sounds like an empty oil drum, the solution is self-adhesive bitumen, the sound from the sub becomes much better, and other noise from wheels etc...
Perhaps there is some hope, the next step is to replace the Hardy discs and center bearing as there is probably a production fault in them, new ones have been ordered and they will hopefully be changed next week, it was found that vibrations/noise are temperature dependent, therefore this...