Cool! Are you going to run with the top up, or down?
Some redneck, yet effective tips for aero are to remove the windshield wipers and side mirrors (not sure how complicated it is to remove the mirrors on a Boxster). Also, use some good quality racers tape (high quality duct tape) and tape over all the seams in the front bodywork, such as the gaps between the frunk and fenders, and around the headlights. I used to race a first gen RX7 that would normally hit about 145 mph at the end of the straight (it was still pulling, the speed was limited by the track, not the car). One time in practice I tried all those tricks, and it actually gave me a few mph. It can't hurt to try!
Ask some of the other racers there who have done this before what other basics you can try as far as tire pressures, etc. May as well take advantage of their experience!