Sorry to hear about your stolen CCs! Hope your insurance is paying for them. I imagine though eventually your insurance will go up (or you'll get cancelled). Ugh!
Not sure if this would stop them, but I implemented a relatively inexpensive deterrent on my 3 RVs after one of the CCs got stolen. Here's a link. Might not be perfect, but doesn't hurt. I've got extra alarms if you are interested (I'm in the Bay Area).
I store my RVs in a yard/field that isn't very well protected, but it is only 3 blocks from my home so the convenience is hard to beat (and it's not too expensive). I poured a base rock pad for each of my RVs. I also took extra base rock and created a mound underneath where the CCs are. This will make it harder for thieves to crawl underneath. That, along with my cable and alarm in the above link make me feel pretty good about my chances of protecting them while in storage and out on the road.
RVs are naturally pretty high off the ground, so CC thefts will always be an issue.