Hi DanJamPer,
Yes ā¦ the softer layer on the bottom could be a contributing factor.
I donāt know the specifics of your foundation but if it has any flex or 'bounce" then it could be part of the overall effect you are experiencing. It could either be a box spring that used coil springs (like this) or torsion springs (like this), or it could be a semi flex or limited deflection foundation (like this) that only has minimal flex. Whether itās called a foundation or box spring is less important than the amount of flex it has and more flex will affect the āfeelā and performance of the mattress more than less flex.
A firm layer of polyfoam and any other āactiveā layers would become part of your āsleeping systemā and thicker mattresses or sleeping systems would be less likely to feel like they are bottoming out yes (see post #14 here for more about the effects of thickness).
This sounds like you are describing the āfeelā of latex itself. Any other active layers that are also highly resilient (such as springs) could also be part of the overall effect you are describing as well.
I donāt have any specific recommendtions other than the list of suppliers that are in the component post here. I would choose based on the type of material each of them have available and on how they compare in terms of price for similar materials.
The opposite of resilience is hysteresis which is how much energy a material absorbs (vs stores and returns). The material that has the highest hysteresis is memory foam so you could also experiment with using a thinner layer of memory foam either under or over your mattress which my have a greater damping effect than polyfoam. It will also depend on the type of movement and the weight of the person and on where you use the memory foam because with larger movements or with deeper compression you will still be compressing deeper layers under the memory foam which would then ābounce backā but with smaller movements or lighter body types the damping effect would be more noticeable. The memory foam would dampen the materials or components underneath them more than the materials above them.
Phoenix