All states are cracking-down on out-of-state registration. I know in California it's probable cause to stop a RV-toad combo when the plates are from different states, e.g. Montana RV / CA toad. Certain things are proof of residency on their own such as where your driver's license is from, where your kids go to school, where you take a homeowner's exemption, etc. I'm surprised Florida is bothering to do it, last I heard, and correct me if I'm wrong, it was $17 to register a vehicle there. It's obvioulsy much more in CA.
