I guess I should have known Alembic would have springs. Conical ones, in fact - not something you're likely to find at the hardware store. And there's foam; maybe to keep the wires from rattling? I pressed down on each pickup, it seems pretty soft so I don't think there's any risk of cracking anything. But thanks for the caution, I'll be sure to press down gently on the pickups when I'm lowering them.
The D/G pickup just needed a gentle reminder that it's adjustable, it probably hasn't been moved in a long time. Raise that one, lower the E/A side a little and the balance sounds much better to me.