I've used the QuicKutz Revolution Scalloped Border dies in my Big Shot. I sandwich the die and CS between the 13" Sizzix cutting pads, the ones meant for the Sizzix long Decorative Strip dies.
I also have the Multi Purpose Platform and 'cos the QK dies are wafer thin, the MPP has to be closed (Tab 2). That means that the dies are longer than the MPP surface - so you don't get a full 12" die cut - you just get the length of the MPP surface. Mind you, that doesn't worry me as I use the scalloped die cuts on cards only, but it might be a problem for someone wanting a full 12" shape for a scrapbook page.
I just use the die and CS between the 2 clear long cutting pads, I've never needed to add shims.
HTH!
Ruth