I installed washers under the rear actuator brackets to correct the locations/heights of the actuators with respect to the shock absorbers. The system in the rear appears to be working now, based on the feel of the damping while bouncing my weight on the rear corners of the trunk. I'll confirm next time I'm on the highway. I put 3 washers under the passenger side bracket and 2 under the driver side bracket. I'm not sure why both sides didn't require the same number, but when I put 3 washers under the driver side bracket the control rod didn't get turned by the actuator (actuator 'too high'). The washers I used were leftovers from another project, so I can't say exactly what size they are.