Hi djgoldb,
It may still be a little bit early to make any significant changes (it’s only been about 2 weeks or so and you have only been sleeping on the mattress with the cover for a few days). You can see an example here of one of the members where it took about 2 months for the mattress to break in and for their body to get used to a different sleeping surface and an initial break in and adjustment period of 30 days isn’t at all unusual.
Again I would sleep on your new combination for more than just one night before you decide whether it is working for you. I would also keep in mind that both layers are compressing simultaneously and not sequentially (the deeper layer doesn’t only start to compress after the top layer is finished compressing) so they will compress and become firmer to different degrees and the top layer will “firm up” faster than the layer below it which generally smooths out the transition between them. It would be somewhat unusual to be able to feel the transition between a 3" 26 ILD comfort layer and a 34 ILD support core underneath it since they are relatively close in terms of ILD.
It may be that you were feeling the firmness of the top layer which may not be allowing you to sink in “enough” on your side to “fill in” the gaps in your body profile when you are sleeping on your side rather than the firmness of the layer underneath it. Most of the “sink” will come from the upper layers (not the deeper support core) so it may be worth trying a 3" 24 ILD layer on top of the support core that you currently have to see if it makes a difference or how it compares to the other two combinations. Your cover may also need more time to break in and lose any of its initial stiffness as well.
It would also be helpful if you let us know whether replacing the 26 ILD comfort layer with the 19 ILD comfort layer resulted in any changes to your lower back pain (you only mentioned how your experience changed with your shoulders) since this may also be a “pointer” to the layering combination that may be best for you.
If you do decide to replace your current configuration with a 3 layer system then I would be tempted to replace it with the slightly firmer of the two combinations you mentioned (24, 28, 36) which would give you a combination where the top 6" of your mattress were both a little softer than the 26/34 combination you started with and the transition between the top two layers would also be very small and then you can use your experience on this combination to assess whether you would need to make any additional changes. I tend to prioritize posture/alignment over pressure relief so when there are undecided between two combinations I would tend to choose the one that is slightly firmer. If you still find that the top 2 layers are too firm for you then you can try the 19/28/36 combination which would be the next increment softer.
In the end though the only way to know whether any combination will be a good match for you will be based on your actual experience and how your symptoms “change” with each combination you try since there really isn’t a formula that can predict which combination will be best for you with any certainty. For most people there is a range of combinations that will work well so they don’t have to find the combination that is “exactly right” down to the smaller details but if you are more sensitive to smaller changes then it can take some trial and error to find the combination that is inside the comfort/support range that is suitable for you.
You mentioned in your previous post that you were also considering a 2 zone system and if you do decide to go in this direction I would make your cut line about 2" above the position of your belly button on the mattress (near the bottom of the rib cage) but playing with different layer thicknesses and zoning systems where you need to cut the latex can become more complex so I would do a little more experimentation with your 6" and 3" layers so you have better reference points before introducing additional complexities into your design.
Phoenix