Hi nativefinn,
You can see my general thoughts about the metal grid type of foundations in post #10 here.
With a mattress with a polyfoam base layer like the Ultimate Dreams it wouldn’t be a significant issue because polyfoam is stiffer and less flexible and elastic than latex and it would provide adequate support but with a mattress that has a latex base layer I would tend to go with a rigid slatted foundation with spacing no more than 3" apart because of possibility that the latex will sink into the gaps over longer periods of time.
Phoenix