Originally Posted by vtjim
That made me think of another suggestion... Run a cable into the trunk and connect it to... Something... Spare tire, maybe?
Then again, the damage a thief would do (to spoiler, or to the paint/metal of the trunk "lid") probably far exceeds the cost of a new rack.
Or just run a cable into the trunk with a padlock connecting the two ends of the cable. With the trunk closed, the padlock won't pull through.