Hi david_a,
I switched your last two posts to a different topic that is more appropriate because our conversation was starting to drift outside of the scope of the original topic you posted in and was more about support systems than the mattress.
You can see some thoughts about flexible slat systems in post #2 here and the posts it links to. A flexible slat system would be an “active” part of a sleeping system (just like any other layer or component either in, under, or over a mattress that flexes or compresses when you sleep on it) so the only reliable way to know whether a flexible slat system would be an improvement for you in terms of PPP compared to a non flexing support system would be based on your own actual experience when you test it or sleep on it in person and compare both types of support systems under the same mattress. For some people it could be neutral, for some people it would be an improvement, and for some it could be detrimental.
A flexible slat system can be beneficial with some thinner foam mattresses (generally two sided) that by themselves may not have enough “give” and/or can benefit from some additional flexibility or “depth” and contouring support under the mattress and in some cases they can be beneficial under some types of innerspring mattresses as well but “most” one sided foam mattresses (and one sided mattresses in general) are designed to do best on a support system that has little to no give (similar to having the mattress on the floor).
Phoenix