I just got my upgraded Aussie backing plates for the rear sway bar installed today. Thanks, Stazi, for the parts. Installation was $40 at Doug's Muffler for you Michigan guys. The install was simple, except that one of the 2 OE bolts being stripped. The plates were welded in and away I went, clunk free. I had battled with the clunk from my 21mm rear bar for almost 2 years but now I have a welded, permanent fix.
For those of you with SCA 21m bars, I used a Prothane bushing and bracket from Summit. These bushings are grooved on the inside for grease retention.
-Kurt