Looks like the weight created new problems that the owner went to great lengths to fix.
They sell a leaded dampening material which is sound insulation and that might be a good idea.
I have to believe the Porsche engineers looked for a lot of other solutions before resorting to that fat suspended weight - adding weight is generally a "last resort" kind of thing. I am guessing it was discovered late in design and they couldn't fundamentally change the hatch in that generation.
It is important to note, however, that it isn't just mass in this case but a MOVING mass that actually responds to movement of the hatch Based on the descriptions, I think of it like a lead fishing weight suspended from a rubber band from solid surface (like the hatch)...bouncing up and down in a DELAYED response to hatch movement. It is anchored more solidly than that of course, but that's an extreme example of the movement.
Finally, one more item. When Tesla updates a part, they SEEM to keep the same part number but change the last digit (usually a letter) to the next highest letter. As an example, part 123-456 will be 123-456-A initially, but if revised it changes to 123-456-B, and so on. Anyway, in the hatch area the online catalog shows a number of parts associated with the hatch with B or C level "revisions". We have no way to know exactly WHAT Tesla changed for any given part, but the reports of this phenomena do appear to be reduced in later cars so MAYBE there is a change that they improved this.
In the attached picture, pieces 5, 7, 8, 9 and 10 are all at B or C level revisions. If you guys have a Tesla gallery nearby you might head to the gallery, pop the hatch on a new Model S and both a.) take pictures of these pieces and b.), see if the rubber stoppers in 10 - particularly 10 - and 7 seem noticeably more or less firm (or if it is more or less firm in its mounting). Last time I was at the gallery I was standing next to a Model X and someone opened the hatch. I noticed the hatch stopper equivalent to #7 on the Model S was markedly more firm on the new X. This made me feel pretty good about my own "solid rubber" mod above. Heck, you could just order the new parts...they might not be that pricey.
There are other revisions in the latch and striker part numbers as well.
Online Catalog (under Model S see section 11: closure components, 1133 Closure Assist Mechanisms and Hinges - Lift Hinges and Fittings)
https://epc.teslamotors.com/#/login