Hi Embee,
You are most welcome! Sorry to hear about the family crisis, hopefully, all is sorted out by now. :unsure:
I am glad that you are getting closer to your desired configuration and that you decided on a side to side split configuration to accommodate your husband. The pillowtop top layer you described has good materials and there are no red flags in terms of durability.
Usually Dunlop makes a better sitting surface and Talalay a “comfier” sleeping surface so it is usually a tough call which way to go, but generally, with most foams, you will sink more when sitting then when lying down. This is because of your weight being distributed on a smaller contact area when sitting than when sleeping. Think of the depth of the imprint of high heels shoes in snow vs slippers. Unfortunately, nobody can have it both ways and the first concern is having good alignment while sleeping which is when the body regenerates and recharges.
How far you sink into a mattress when you are sitting upright has very little to do with the support of a mattress which is designed for the weight distribution of a person when they are lying down. Latex, in particular, is so point elastic that you may sink in deeper when you are sitting on it and the weight is more concentrated (the material beside the point of compression has less effect or “drag” on the material that is compressing) and yet this same soft material is also very supportive and can provide good alignment when you are lying on it. Support (the ability to bear weight without bottoming out) is a means to achieve alignment when you are on a mattress in all your sleeping positions but neutral alignment is the goal and support in each area of the body is just the means to alignment … not the goal in itself.
The core’s primary function is connected with support and keeping the body in neutral alignment and only secondarily with comfort. Alignment itself is quite complex and involves different factors. The most important is spinal alignment from top to bottom of the spine and maintaining the natural curvature of the spine however it also involves “side to side” and “rotational” alignment and the alignment of the joints all of which can have a “natural” or “neutral” position along with a “learned” position. All of these interact with the ability of a layer(s) to re-distribute weight throughout the surface of the body in each sleeping position (and there are many variations of the 3 basic positions).
Your choice of a soft pillowtop will “allow” these types of positions more easily because of the characteristics of the foam. Latex has a higher compression modulus or “sag factor” than polyfoam and also a higher resiliency (stores more energy instead of absorbing and dispersing it and “bounces back” more readily). What this means is… people who have good posture both top to bottom and side to side will be more supported in this “good posture”. Those who have a more “learned” posture (or even a natural posture or body type or weight distribution that is outside of the “norm”) may have a feeling that the latex is “pushing back” as it tries to even out the alignment in all directions as opposed to poly and memory foam that will “allow” more sagging into the material.
There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here about firmness and support and in post #4 here may be helpful in clarifying the difference between mattress “support”, “pressure relief” and “feel” and it can also provide some useful insights into the reasons for pain and/or discomfort on a mattress.
Children have different support/comfort requirements than adults do. There are some links to the better forum posts Included in Post #2 here with topics about mattresses and children and includes some suggestions and guidelines and links to some good quality/value options as well.
I’d also make sure to revisit the Mattress buying personal value equation to help determine all the parts of that are most important to you.
Once you cover some of the readings I linked above you’d probably have enough information to move along in the decision process. Let us know how it goes.
Phoenix