Hi txjeff,
Welcome to the Mattress Forum!
The short answer to your question is…yes. A firmer layer (density and firmness are not the same thing), or a change in surface layering, can certainly cause such an issue.
Having a softer topper certainly can assist with your overall comfort and pressure point relief, and while memory foam and latex are highly point elastic, they have different properties. Both of them come in a wide range of different versions that each have differences in their properties and a different “feel” or firmness level but the choice between them is more of a preference and budget choice than a “better/worse” choice. There is more about some of the general differences between memory foam and latex in post #2 here. Some people tend to prefer the faster response and more resilient and “on the mattress” feel of latex and some prefer the slower response and more “in the mattress” feel of memory foam and some people may prefer some combination of both of them but the only way to know which one you tend to prefer in general terms will be based on your own careful testing in a store or your own personal experience when you sleep on them.
It sounds like you’ve created an entirely new mattress versus your old product, and since all layers work together, there certainly could be causes in the deeper layers that are also contributing to your pressure points and surface “softness”. The most common definition of softness has to do with the pressure relieving qualities of a mattress. This comes from the upper layers of the mattress and how well they re-distribute weight away from any pressure points. If you read post #6 here it describes someone floating in the air in good alignment and gradually being lowered onto a mattress. At first only the more “pointy parts” of the body will contact the mattress and all the weight is concentrated there. As you gradually sink in deeper more of the body surface begins to take up weight and relieve pressure on the parts that were initially in contact with the mattress. Eventually enough of the body surface is bearing weight that there are no perceptible pressure points. This is why the depth of the pressure relieving cradle and the materials that are used in the top layers are so important.
Generally … if pressure on the surface capillaries in the pressure points are reduced to below about 32 mmhg (a unit of pressure) for most people, then the capillaries won’t collapse with the pressure and the blood flow will be maintained. When this is achieved … the body doesn’t feel “pressure” or the urge to move and restore blood flow. Once you have reduced the pressure on the pressure points to the maximum possible … then there is no further benefit to sinking in any more. If the heavier parts keep on sinking because the comfort layers are softer and thicker than you need to achieve maximum pressure relief … then all that happens is that you lose alignment with no more benefit of more pressure relief.
Some people need more pressure relief than others because they are either more sensitive, have less muscle tone, sleep in more pressure prone positions, or because their capillaries “collapse” more easily for various reasons. These people will generally do best with the maximum possible depth of cradle that is beneficial but more than this introduces new risks for alignment that have no pressure relieving benefit.
In some cases … some people just prefer to sink in more deeply into the comfort layers and as long as this is done evenly without one part sinking in too much relative to the rest … then this is a matter of preference.
It’s possible that simply changing out the upper layer of your current mattress may alleviate your pressure issues, and certainly that would be the logical place to start. But with a wholesale change to entirely new components in your new creation, it’s possible that you may also end up needing to change the “transition layer” underneath the top layer as well. This is always the interesting part (and sometimes frustrating part) of a DIY mattress.
I’m interested to learn how changing the layering works for you.
Phoenix