Hi kchurch2213,
Referencing back to one of my replies to you earlier, there are too many unknowns, variables, and personal preferences involved in choosing a mattress for someone else to make specific suggestions based on specs (either yours or a mattress) or theory at a distance that can possible be more accurate than your own careful and objective testing (using the testing guidelines in the tutorial post) which is always the most reliable way to predict which mattress will be the best match for you in terms of PPP (see mattress firmness/comfort levels in post #2 here). Making more “educated guesses” about layering combinations or changes that may work for you is really a process of “differential diagnosis” that relies on using probabilities and some trial and error in combination with your feedback and assessing how your actual symptoms change and either get “better or worse” with each layer combination you try. In the end, there is no “one best” memory foam configuration, only one that “feels best” to you.
As it seems you are attracted to the idea of designing and building your own DIY mattress out of separate components that are purchased from one or several different sources then the first place I would start is by reading option 3 in post #15 here and the posts it links to (and option #1 and #2 as well) so that you have more realistic expectations and that you are comfortable with the learning curve, uncertainty, trial and error, or in some cases the higher costs that may be involved in the DIY process. While it can certainly be a rewarding project, the best approach to a DIY mattress is a “spirit of adventure” where what you learn and the satisfaction that comes from the process itself is more important than any cost savings you may realize (which may or may not happen).
As a start I would use the specs (if they are available) of a mattress that you have tested and confirmed is a good match for you in terms of comfort, firmness, and PPP as a reference point or blueprint and try and “match” every layer and component in your reference mattress as closely as possible, or alternatively use a “bottom up” approach (see post #2 here). There is more information in post #9 here about the different ways that one mattress can “match” or “approximate” another one. Every layer and component in a mattress (including the cover and any quilting materials) will affect the feel and performance of every other layer and component and the mattress “as a whole” so unless you are able to find another mattress that uses exactly the same type of materials, components, cover and quilting, layer thicknesses, layer firmnesses, and overall design (which would be fairly unlikely) then there really isn’t a reliable way to match one mattress to another one in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your Personal preferences) based on the specifications of the mattresses (even assuming that you can find out all the specifications you would need for both mattresses you are comparing in the first place). But as a reference it can be a good starting point and “get you close”.
Ultimately, the only way to know whether any specific mattress design or combination of layers and components is a good “match” for you in terms of comfort, firmness, and PPP with any certainty will be based on your own careful testing and/or your own personal experience when you sleep on it. Having said that … you can see some general comments about the properties of an “ideal” mattress in post #4 here.
This would be a personal preference and would also allow for a bit extra room for customization. You will find that there are many memory foam manufacturers who use this approach to more closely “match” and allow for a more gradual “bend in” for the layer above it. Some will also use some sort of a shaped foam in this upper polyfoam piece for increased air circulation.
Again this would come down to your own personal preference. The nice thing with a component system is that it is easy enough to try one layer over another and then switch back. With memory foam, you’ll “usually” find companies in a configuration like this placing the less dense foam over the more dense, but you certainly could use the more “dominant” layer on top for a different feel. Of course, there are many different types of memory foam available with different rebound rates, response rates, formulations, additives, ILDs, etc., so this could also influence your decision of which layer feels best placed one over the other.
Phoenix