Disable the interior trunk lever via the orange lever in the trunk. Beef up your alarm, ie. if you don't have a hood pin switch, get one, invest in a good air horn and get your horn honk out put hooked up, proximity sensors rock if hooked up and set right, i would also invest in a backup battery for your alarm if you are that worried about your stuff being taken. Now this may not prevent a theif from stealing your stuff, but it might deter 90% of them when they get close to your car and your air horns start blazing to warn them off! I must warn you though, the motion sensors can get annoying, but to me it is worth the trouble of looking out the window for no reason.