Hi redditmike,
I don’t think you’re understanding how the foam is described. You’re not measuring the total weight of a mattress – you’re looking at the density (mass per unit volume) of each layer of foam. You provided the density of each layer of foam in your earlier post.
You’re welcome to question it :cheer: , but I’m not a “reviewer”, and while I’m constantly offered free mattresses, I don’t accept them.
Most modern mattresses “fail” due to the low quality foams they use, not the foundation. Most modern brands use rigid metal semi-flex cages or wood foundations for the base, which usually don’t fail before the low quality foams within the mattress, which is most likely what your old mattress and your current mattress contain. Now, if you are using an actual old coil box spring unit with a mattress, that will contribute to premature sag in most modern mattresses. And you need to make sure that your bed frame has a reinforced center beam.
Regarding an appropriate foundation, everything you need to know if explained in great detail in the foundation thread here.
Phoenix