Tough question with one answer... it depends? How soft or firm do you want to ride to be? What is your driving style, do you have a wife or girlfriend that may or may not like a firm ride. So many variables.
Here's a middle of the fence answer, depending on the difficulty level in adjusting after the install, I would set them to "5." Let's just assume 1-10 is the variable. This would put you in the middle. Drive your car, see how you like or dislike and adjust accordingly. Make sure you drive it in all the variable terrain and roads you will encounter as well as the person who may ride with you.