How to improve Park Brake Performance with Dr Diff Rear Wheel Disc Conversion?

Lube the slide pins, cables, equalizer, and hand brake. Clean the pads and rotors. Scuff the rotors. Support both the rear wheels off the ground, have someone apply the brake pedal and check for rotating resistance on each wheel, then set the parking brake, hands on the tire or a lug wrench to compare effort from side to side and equalize. Look at the arm on the calipers to see if they are rotated the same and have not run out of travel/hit the stop.

Caliper type parking brakes do not hold very well compared to drums. Larger cars typically have a small drum in the rotor just for parking.