Afternoon Clemens, I did not take any pictures when I applied the neoprene strips, but I am going to take the undertray down this winter, so will take some photos then, It does not take much to stop the vibration as its just in a few areas on the tray.
Interesting ref removal of the centre section of the exhaust not making any sound difference, that mid exhaust silencer is a Helmholz resonator box to dampen specific frequencies. Guess only the factory knows which and they must have added it for a reason..