Hi Mike77,
I don’t have any specific suggestions because the first “rule” of mattress shopping (or mattress surgery) is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and your Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more accurate than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
I also wouldn’t focus on whether a mattress uses a “differential” or a “progressive” construction because these are only very general and broad descriptive terms for how a mattress is layered and there is no inherent reason that either one would be better or worse in terms of PPP and either one could certainly make a good choice depending on the specifics of the materials and components and the overall mattress design and layering.
If you are attracted to the idea of designing and building your own DIY mattress out of separate components and a separate cover (which in effect is what you are doing if you are doing “mattress surgery”) 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).
There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel” that may be helpful as well.
There is also more about mattress surgery in post #2 here and the posts it links to that may also helpful.
Every layer and component in a mattress (including the cover and quilting) will affect the feel and performance of every other layer above and below it and the mattress “as a whole” so it would really depend on the body type and sleeping style of the person and the overall design of the mattress.
Assuming that the materials in a mattress you are considering are durable enough for your body type and meet the quality/durability guidelines here relative to your weight range … the choice between different types and combinations of materials and components or different types of mattresses are more of a preference and a budget choice than a “better/worse” choice (see this article).
The component list here includes the better online sources for polyfoam that I’m aware of (and includes foamonline) and there are also some comments and comparisons in post #4 here and post #6 here that may be helpful as well.
I don’t know of any local polyfoam suppliers in Vermont off the top of my head but New England foam is one of the suppliers on the list and they are in Connecticut although they have a minimum order of $200 and you would need to check their prices for the specific foam layers you are interested in.
Phoenix