Victory!
I decided to start with the just the lower flippers in upgrading my Black Knight flipper mechs. The old flipper assembly brackets do not have a tall enough bracket to mount the spring onto, so I had to order new brackets and install them. I learned one important lesson. If you reverse the wiring, you blow the diode on the flipper coil! (as well as the 15a fuse in the backbox!) After a trip to Radio Shack, and future-proofing future mishaps with a purchase of a 25-pack of mixed diodes, we are back in business. It plays great, and the left ramp shot off the right flipper is stronger than ever. Again, the biggest gain is not in strength, but in agility. You have more control in the flipper area for carving the edge of the most near-middle ball rolls into the flippers, and you can make some crazier saves with the newer flipper mechs installed.
Will post before and after videos tonight!