We have a 2017 Sunset Trails 291RK (rear kitchen) and I have been doing some fixing/mods. I found about 2" of styrofoam with plywood (can't remember if 3/4" or 1/2"). I could see how thick the floor was at a place where things like water and electrical went from inside into belly. After I put foam pipe insulation on all pipes and added actual insulation to inside frame and under plastic in belly, I used foam-in-a-can to plug the holes into belly. I also added an extension to the 2" vent from furnace that came out into the underbelly but BEHIND the rear gray water tank. I extended it forward with PVC pipe and drilled large holes at an angle to direct airflow foward. Now it actually is a better "Extreme Weather package". So anyway the floor in this one is around 2" thick and has a nice solid feel.