Hi marvin gardens,
Post #2 here has links to some of the theory involved in mattress layering but there are too many unknowns and variables involved to make specific suggestions for any particular person and this is only generic information that can be helpful as a general guideline
The best way to choose your layering is with your own careful and objective testing using the testing guidelines in post #1 here. Your own personal experience is a much better way to make the best possible choice in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) than any “theory at a distance”.
Phoenix