Sounds from your description that there is no belly pan on that trailer (in that area at least) if you can see a waste tank. No belly pan...no insulation, but you can check the frame for rust or severe corrosion I believe.
A wise man once told me he wanted to stay fit enough to run a marathon on his hundredth birthday. Another said he wanted to be shot by a jealous husband on his, I'm with the latter. God bless you Richard.
Carpet Cleaning is what I do, it's not who I am.