This is kind of off subject but I would not worry as much about the tank, per se. The tank usually is going to be somewhat flexibile and have room for the contents to expand. Rather, I would be concerned about the dump valves and their associated piping. As I see it these are the places that will be full, with no room for the contents to expand to relieve the pressure.
Happy Camping! ///// Richard D.
2006 4x4 Ford 250 SD / 2007 Flagstaff 827 FLS
One very patient wife and one furry child who travels with us. Forty-two years of trailering and camping, and I still have a blast.