I will preface this by saying that I boondock or remote camp 99% of the time (my closest neighbor can usually be seen through my binoculars). As such, I carry a full tank of Water everywhere I go.
Although I have three angle iron supports for my freshwater tank, it develops a serious "belly" that sags down in between when full. Also, the tank material is surprisingly thin. I would say less than an 1/8". As I'm considering how to address this in terms of adding support, I discovered what appears to be sharp welding slag that was eating away at one corner of the tank.
I smooth out the angle iron. However, I'm seriously thinking about replacing the tank given the type of camping I do. I'm considering replacing with the brand Recpro as the walls of their tanks are 1/4" thick.
Stay tuned as I update this thread on what I ultimately do.
Take care!