When I upgraded our black tank I did a lot of research into holding tanks. The most common mounting method I've seen is using 2 'ears' molded into the top of the tank along the long side. The standard seems to be (such as it is) is 3" tall by 1.5" deep. On my trailer (and I suspect many others) a length of angle iron is bolted across the frame supporting the tank via the ears.. my tanks rear most 'ear' is supported by a frame cross member. In my case the angle iron support is plenty strong.
One manufacture (Inca) recommends that at least 3/4" of that 1.5 inch ear be supported. If both ends are supported 3/4" the entire tank could shift for or aft and drop out of the other support. I haven't checked to see if that recommendation still stands.
Black tanks tend to be kept from moving for/aft by the toilet flange mounting. Gray tanks perhaps a bit by the drain plumbing. Fresh water I would think is less likely to be secured by the fittings.
Add to that tank manufacturers changing designs constantly, which I know for sure they don't test well at least in one case (Inca H183, rated 11 gallon tank in 2013, in 2014 de-rated by the manufacture to 7.25 gallon, actually holds 5 gallons).
I'm surprised that tanks hold up at all!
And I agree that withholding manufacturer/model information does the community a disservice. If this happened, it happened. Nobody is likely to take a single incident and use that as as sole determination.
