Bend pin 18 for the top down hack. You still need to engage the parking brake light, not the parking brake itself.
Are you looking for cosmetic or performance mods? There are several things you can do really, depending on what you want from your car.
For cosmetic touches, you could paint the bumperettes at the back of your car to whatever color the panels are, this makes the car look somewhat younger.
You can also add the Cayman spoiler to the Boxster, I personally think this adds a bit of style to the normal wall that is the stock spoiler.
Aftermarket Spoiler