you can use the factory struts. If you run the lowest setting, you will blow the struts, but that will actually will make the car ride better since some of the pressure will be released. I ran my P5 4" lower and they released some fluid about 500 miles. Before that they were bouncie, after that it ran smooth. You do have to cut the bump stops, but if you need to return to stock is no problem. The bump stops will be hidden from view by the dust boot cover. I did sell the P5 in stock form and it rode pretty well afterwards.
vic