You must have insurance issued by a Florida insurance agent, which will probably require some type of an address to acquire. After that, it will be no problem registering the vehicle in Florida.
Now what South Carolina will say about your Florida registration is the big unknown. Why not call the SC DMV and ask them what happens if you get stopped with a SC driver's license, showing a SC address, and you are driving an RV registered in your name to another address in Florida. This not a problem if you are in the military, but since you are not, it may be a big red flag.