Hey there!
Let me start with congratulating you on the color choice! Quite stunning
As for the noises - I haven't found a solution. However, I love the tape-and-test approach! I will try it as soon as the weather improves a bit. Hopefully, this will allow me to locate one part of my "noise problem" - the wind hum which appears at the base of the A-pillar and which is audible along the entire length of the window frame (rising towards the roofline)
I suspect the tape approach won't do much good in terms of fixing the other problem, i.e., the sensation of hearing the passing-by traffic. It's a bit disappointing that my 7-series doesn't handle this issue as well as even my cheap Opel and not-so-cheap Volvo did...
I'm pondering a more extreme approach, however the cost quoted by some sound insulation experts had dampened my eagerness to go ahead with it for now... The quotes I got (roughly EUR 2.5-3.0k) cover a thorough cabin insulation; during which they pretty much take the car apart, leaving only the dash intact (everything else is stripped to bare metal - including roof lining, floors, doors, the whole lot - and covered with sound-proofing materials; the same is done to window mounts, door seals, etc.)
My brother got his G31 (5 series wagon) done this way. I haven't yet tested it, but he seems happy with the results. I'll wait with my verdict until I've driven his ride after the operation
I'm curious to learn what you find during your tests!