I used to have the same fear until I upgraded to a Medium Duty Tow (MDT)vehicle.
It's quite different feeling when stopping the MDT with the 5th wheel in tow. The weight of the MDT, power of it's brakes and exhaust brake all work to make the stop quick and controlled. It wasn't like that with my previous 1 ton Dually. I always left big gaps and stayed under the speed limit when in town to give me the best chance at panic stopping if needed.
I used to watch the big semis towing a trailer on city streets and was concerned at how fast they drove and how late they would stop for a signal. Now I know the drivers were confident due to the ability of their trucks to bring a load to a quick and controlled stop. The right setup will make the difference.
To learn how my RV's react I always head for a deserted road or large empty parking lot. I do panic stops, quick lane changes for avoidance, turns and parking so I will know what to expect.
