I've only done 3 big flushes, one recently and 2 five years back. All the 'stones' after the flushes have floated, even the large ones I've seen most recently. The first time they were green chickpeas, then second was tan 'chaff' (like tan split lentils), and the third were grape sized green chickpeas encrusted with tan chaff. Go figure ;)
I know I've read Miss Helfinger drinking a certain decoction during her IP, and unexpectedly seeing stones, so it seems possible with a high quality liver tincture.