The thing you have to remember about theft protection is that there's really little you can do to stop a serious, professional thief. However, those guys are rare; the huge majority are dim bulbs who are just looking for a fast, easy score. (And, at least in S. Cal, there's the joy riders, who fall into pretty much the latter category.) Do anything to make the car even moderately difficult to steal, and they'll go looking for something else.
Here's my story: some time ago, I bought a Toyota Van, which had an externally mounted spare tire that was notoriously easy to steal. Knowing that, on the way home from the dealership, I stopped at a K-Mart and got a bike chain. Put it on the spare, and tucked it away out of sight. FIVE TIMES in the next few months someone tried to steal the spare--popped the catch, found the chain, and left. Never got the tire. The chain wasn't difficult to get past--a simple bolt cutter would snap it easily. But no one wanted to take even that much time or go even to that much trouble.
Finally, I draped the chain so it was visible at a glance, and NEVER, in the following six years, did anyone even try for the tire. Finally someone stole the whole car, so I guess you could say the spare eventually was stolen. Sigh.