I replaced the entire element in the drivers seat bottom today. Overall it took 2.5 hours, taking my time and using this thread and the vacation pix as a guide. Thanks to the OP for putting up the steps and pictures.
Here is the other waist spoiler from japanparts:
http://www.japanparts.com/db/parts_detail.php?NUMBER=00013030&VOLUME=107-112-016&DEALER=1&CAR=141&MIDDLE=2&SMALL=11&MAKER=5&VOLKEY=&SEARCH_DEALER=1&SEARCH_CAR=141&SEARCH_MIDDLE=2&SEARCH_SMALL=11&SEARCH_MAKER=&SEARCH_VOLKEY=&SEARCH_page=5&submit.x=41&submit.y=6
Mine was not as high a frequency as yours, alanztalon. The right way to fix it is by taking it all apart. like the OP did. It didn't take me long to do, and I used some leftover sound deadener material to keep the rattle from ever coming back.