Hi sleeplessinNYC,
This is a good diagram I have often linked in the forum but it’s difficult to actually see every curve of the spine so I usually use a more combination approach that looks at “symptoms”, and “eyballing” the overall look of the body profile along with general information about the mattress and the person to get a better sense of what type of changes have the highest probability of success. Once you are past the more simple and higher probability solutions though … things can get incredibly complex for the minority of people where simple solutions are not successful because each person has a different natural curvature and a different physiology so getting too exact with the actual curvature of the spine can sometimes be counterproductive when their natural alignment isn’t in the “normal” range. In these cases it becomes more of a medical issue or body structure / physiology issue than a mattress issue and starts to go outside what is possible to help with on a forum without more professional help.
Pillows are an important part of overall alignment on a sleeping system… and they particularly affect upper body issues like the upper back, neck, and shoulders. There is more information and links to some good resources in the pillow thread here. Like mattresses … there are some basic “needs” with pillows based on body type and sleeping positions but personal preference plays a much larger role with pillows than it does with mattresses and the overall “feel” of a pillow can be much more important because it is in such close contact with a very sensitive part of the body (the head and face).
Yes … Dunlop and Talalay will respond and feel quite differently … particularly if the layers are thicker. Dunlop has a higher support factor (gets firmer faster) than Talalay which can change how the mattress responds significantly. If the two layers of “medium” Dunlop were the same ILD as your 6" of Talalay then they would tend to feel firmer for most people and would also be more supportive in terms of how well they held up your pelvis. The “medium” Dunlop probably has a higher average ILD than your Talalay as well. 6" of medium Dunlop with 3" of “soft” Talalay is a fairly common construction that many people do well with.
When you have a thinner layer of softer foam on top and then a firmer layer underneath that … what you feel is a combination of both layers because the firmer layer underneath will “come through”. If you were to use an even softer top layer for example it could feel even firmer because you will sink into it and “go through it” more and feel even more of the firmer layers below it. This is just one place where mattress design can be so counter intuitive. Layer thickness plays just as big a role as layer softness designing a mattress. It also depends on which type of “softness” people are more sensitive to and they feel the most (see post #15 here).
I would be very careful with this. I assume your mattress is probably on the floor or on some type of non fleing surface and if you add even firm dunlop underneath it it will have more “give” than the surface your t" of talalay is currently sitting on and make the overall mattress even softer (the Dunlop is softer than the floor). I would think what you probably need is a firmer layer closer to your body (say 3" deep in the mattress) which isn’t really possible with a 6" layer on top. Again the thickness of your layer and the position of your layer is the difficulty you are facing. If you only had 3" of 28 ILD it would be easier to use firmer layers underneath it to improve support/alignment because your mattress would get firmer faster as you sank into it but the layers on the bottom have the least effect and won’t stop the top 6" (which is where the majority of the mattress’ performance comes from) from being too soft.
Perhaps the option with the highest odds of being a “possible” fix would be to use an inch (or two at most) of firmer latex on top (thin enough that some of the softness of the 28 ILD Talalay still comes through but thick enough that it reduces the amount your pelvis is sinking in). The other side of this though is that it may introduce pressure issues even if it helps with alignment because it would also reduce the amount your shoulders are sinking in and you would be on top of a firmer layer. I would even be tempted to use an inch of firmer latex (which will help reduce the amount your pelvis is sinking in and may still be thin enough for your shoulders to “go through” it into the softer layers below) and then put a wool quilted stretch knit cover around this (the wool will also firm up the surface compression a bit as well) but all of this would be a lower probability solution than a progressive design with a thinner comfort layer and firmer latex underneath. I would even consider using a thicker wool topper on top of this to further reduce the compression (the wool will “pad” your pelvis area and increase its surface area which would reduce compression). In all of this though I would keep in mind that you would be spending your money on untested combinations that may surprise you in how they interact with your body type.
It’s usually only less costly if you make every choice of layer correctly. As soon as you buy a layer that doesn’t work in your design and can’t return it, it generally becomes a more costly method than working directly with a manufacturer where you can choose your own components and exchange the ones that don’t work for a minimal cost.
If you are buying something that you haven’t tried in person … then it’s important to always ask “what options do I have if I make the wrong choice?”. This is a big part of “value” in an online purchase. if you are local and you can test layers before buying them , then it’s different because you can have a good idea of how it will perform before you buy it.
Two sided mattresses are more durable and can last longer … and yes we flip and/or rotate it (usually every 3 months but sometimes longer). The soft on the bottom is more of a liability than a benefit and needs to be taken into account in terms of how it interacts with the rest of the mattress and the people on it. It’s just a side effect of a two sided design where there will always be a softer “comfort layer” on the bottom and is just one of the tradeoffs involved in every mattress design.
Phoenix