So the problem is that only 2 of the strings have the distance from the bottom of the string to the top of the pickup that you desire? Are the screws too short to get the pickup heigh enough for your needs?
Normally I wouldn't put the pickups close to the strings for a heavy handed player, since then the string can easily bottom out on the top of the pickup when you get excited and play super hard. Do I understand correctly that you want the radiused pickup to help you play less heavily?
Adriaan is right that adjusting the height of the pickup will change the sound. It's hard to describe, but the closer the pickup is to the strings, there is less noise. It's also louder when it's closer, so if your Alembic has 2 gain controls inside, you'll probably want to
adjust them to balance the volumes of the two pickups.