I have towed my 3500 pound I/O boat in my signature behind my 5th wheel. As a matter of fact down there in your state. I have done this about 1/2 dozen times. My boat trailer is wide enough I can see the wheel wells in my mirrors. I was pretty long. It is not my favorite thing to do and now I much prefer trailering behind my TC. People do it all over the place in my neck of the woods. I did notice some swaying back and forth of the boat trailer. I always traveled at or below 55 mph. You just want to be careful where you pull of the road make sure you have plenty of room for your turns.
JMHO