Hi rictorjr,
This would be a pressure issue which is different from an alignment issue. I wasn’t suggesting that you only use the 3" layer over the core as a final design but that testing whether it made a difference in your back symptoms and assessing how your symptoms changed would provide a valuable reference point. For example if you found that your back (alignment) issues are better even though they are replaced with pressure issues it would give you some valuable insights into the type of changes that may work best for you.
Having said that … if you are confident that you need softer comfort layers then of course that’s the direction I would go.
Based on the specs you listed it sounds like your layers may be “natural” (which uses a blend of natural and sythetic rubber) rather than “all natural” (which uses 100% natural rubber).
There are some good sources for any type, thickness and ILD of Talalay you may need in post #4 here (KTT Enterprises and Sleep Like a Bear both carry all the LI options).
Phoenix