Just remember, you are trying to "secure" something that is only slightly stronger than a large, double strength cardboard box, no matter what type of RV it is!
There are very few things that can be done to deter a thief that is truly dedicated to separating your goods from you. While it may be possible to slow him down or annoy him, if he wants it he will get it!
While a booby-trap is always tempting, be aware of the liability laws in your locale. Such a trap could end up costing you more than it saved!
Other than that, there have been some pretty good suggestions in this thread.
Don't be too disappointed when, in the final analysis, they do little or no good. That's simply life in the modern world!