Just normal driving, the trailing arms go up and down with the humps, bumps, dips, speed bumps, drive ways etc... a lot more than a few milimeters the springs pad would change.
we just came back from a short trip. had the car loaded down with luggage etc.... and my 5000# tool box

, and she was squatted down pretty good.
we need a poll, long hoods vs short hoods, or no see hoods

.
Charlie