I run ST4S plates in my Corse slipper without any problems at all.
Not all the slippers are made in Italy. There are a lot of copies coming from eastern europe and these are the ones to stay away from.
Trouble is, there's no easy way to spot them until they start to wear quickly. They don't pay too much attention to copyright laws either
STM are/were doing a promo on the Classic slipper inc. plates for £650 and also a couple of deals on the Evo's but you still need the either 12T or 48T plates with those. Don't know if there are any stocks of the promo gear left? I've sold all mine.