Well, I was one of those 300K Americans that decided to file an ATF Form 1 to register my SIG MPX with PAB as an SBR. Back in Feb/Mar/April/May, I watched the news and YouTube to see how several lawsuits against the ATF's PAB ban were progressing, and it was getting discouraging. Just before the "grace period" ended on May 31, I filed my ATF eForm (to take advantage of not having to pay the $200 fee). I just received my "Approved" form from the ATF via email on Aug. 16 (10 weeks of ATF processing- not bad!), stating that I now had a registered SBR. I'm OK with my decision because I can now shoot my modified MPX anytime without worrying. And I can put whatever SBR accessories I want on my MPX. I still hold out hope that the ATF's PAB ruling (and their other ridiculous rulings) will be overturned by the Courts.