Hi hose406,
You can see my thoughts about designing your own mattress vs other alternatives in post #15 here.
I would also keep in mind that a mattress that is suitable for one person in terms of PPP (Pressure relief, Posture and alignment, and Personal preferences) may be completely unsuitable for the next so I would be very careful duplicating anyone else’s mattress unless you have tested that specific combination of materials and know they are suitable for you in terms of PPP…
Because you won’t have the guidance of a specific manufacturer that has mattresses with known material combinations that they can match to different people based on “averages” of others that may be similar to you … this approach will take extensive testing on different types of materials and different styles of mattresses so you have enough experience to first know what combinations are most suitable for you and then source the same materials in the layer thicknesses that are as close as possible to the ones that your testing shows you do best with.
Post #2 here along with post #2 here about “specs” post #14 here about some of the challenges that may be involved both in terms of finding out what is in the mattresses you are using for testing and being able to match them would be well worth reading. The mattresses section of the site also has a lot of more detailed but generic information that may be helpful.
It will also depend on where in the “design sensitivity range” you are with “princess and the pea” being on one end and “I can sleep on anything” being on the other end. The closer you are to the “anything” side the more likely your odds of success. On the other end of the scale I wouldn’t suggest it at all.
Phoenix