This time I've got it.
I wasn't entirely satisfied with last night's attempt because it was too flat, and didn't have the domed quality that the earrings and smaller rivoli-less pendants had, because of the size of the large outer beads. The length of the bead holes of the large outer beads to be precise.
So if you use a bead that is fatter than it is tall, you can move the shape of the pendant towards the convex and away from the flat, while still at the same time have plenty of bead peeking through the seed bead overlay.
Not to mention that somehow it seems that Jablonex uses its very best, most gorgeously funky colours for the rondelles. The round beads are all pretty meh by comparison.
And while I was at it, I fixed the edging which was fine before, but relied too heavily on thread tension. A small change produces a more dramatic shape with less effort, so now my work is done.
I wonder if the rondelles would work for the earrings...