Hi JBB0,
Welcome to our Mattress Forum! 
Your approach to designing your own DIY is certainly very creative and you have some innovative ideas with which would be probably better served in a product development environment. Thanks for taking the time to create the graphics that go with your DIY… Every great idea was born as in response to a certain need.
Because there are so many variables and personal and subjective perceptions the right answers to your questions would come from your own testing and from the way your body will respond and interact with each of the layouts over a long enough period of time. I’d certainly continue in the same scientific manner you’ve started and perhaps keep in mind a few things while you go through the testing period.
- I’d make sure to change only one variable at a time and to keep a record your observations and findings but also give the change enough time for the real effects to “settle” in before moving to the next build.
- Assess each of the layout designs for more than a week or two before you decide if it is a good enough fit… you’d need to give your body a chance to adapt to the new sleeping surface and unlearn and let go of any “postural fix” that the body trained itself to “learn” in coping with any postural stress before returning to a state of “normality”
- Keep some notes of your experiments with both quantitative and qualitative data to help testing comparisons . (things like … how long it takes you to fall asleep … duration of your sleep)
- It would be also helpful if you’d have some type of monitoring device that records your movement during the night .
- Although any qualitative type of assessment is more inaccurate some good indicators would be how well and energetic you feel in the morning and so on and the level of pain on a scale of 1-10
Regarding your pains in the morning especially if they are “entrenched” or chronic I’d keep in mind that you’d need much longer adjustment periods when you make any changes and that some gentle coaching of the body, tissues, and joints to destress and relax. There is a good article by Paul Ingraham about some causes of back pains here and you may also want to check out some interesting facts related to body alignment here and here.
A few general thoughts about your designs:
While propping up the lumbar area with a firmer zoning for added support might work well in some cases, designs C and E would probably have the least chance of success even if the combination was just right to fill in the lumbar area gap… the apex of the firm “pyramid” under your lumbar would place your body on a sort of fulcrum and any small shifts that come with normal repositioning during the course of the night will throw off this arrangement. We commonly reposition between 20 to 40 times (even if people don’t often recall it) and this type of design could “lock” you in a certain position that is most likely difficult to maintain for too long. Whether awake or asleep the body is always in motion and both minute oscillatory and larger movements occur in all body parts. There is an analogy in the comfort section of the basic functions of a mattress article here that talks about this in more detail
I won’t be able to tell how much thickness would be enough to relieve your shoulder pressure points but the chances are that your shoulders would go right through the 1" of 20 ILD to the 4" of 30 ILD which could be a bit too firm for a (60-70%) side-sleeper…. But again, this depends on your preferences, needs and body shape. I’d say that it’s worth experimenting with a little more plushness for your shoulder pressure points.
This is a good starting point that would allow you to collect enough data points before “cannibalizing” more of the layers It looks like fun and it’ll be very interesting if you could document the results of your testing and share it with us. You certainly have many layers to play with to find a good combination that works well for you.
Phoenix