I put the Safety Plus on my Diplomat and found that all it did was cause more arm fatigue because it took more to turn the wheel.
I sold it and bought the True Center. The True Center has a dash switch that allows you to correct for road crown and wind conditions. I installed on the Diplomat and then left on a 6000 mile trip. When road conditions change, you momentarily push the True Center button and the coach tracks straight no matter what the conditions. Within a 100 miles of installation, it became second nature to use the system.
It's twice the price of the Safety Plus, but well worth it.