This is one of those things that just went a bit too well.
To be fair, it was almost a catastrophe as the trough almost didn’t fit. It’s practically friction fit in against the flipper base. However even with such a narrow margin, everything lines up OK. I was even able to re-install the old back plate around the new assembly so the ball doesn’t fall through the back of the PF. It’s insane how well this all worked out, given how drastically different the old two solenoid williams design is from this modern Stern assembly.
As you you can see, even the old skirt fit back in with zero modifications. It looked like the outhole was going to clip a bit but it clears just fine. I’ve not figured out what to do with the old second solenoid yet (Maybe a flash lamp?), and I haven’t found a good hole in the matrix to squeeze in the jam opto; but it’s not super critical.