I always use two jacks-i can recommend SGS Tools for these,good quality and double piston.
Best to purchase a low profile type for the Boxster-or alternatively drive onto scaffold boards to give you extra ground clearance.
Look on Utube for an article by "road and race" on how to jack up a boxster-very informative 🙂
As 1/2cwt says-if jacking the rear REMEMBER to chock the front wheels.