Hi brc722,
You’re right that neither of these mattresses have any weak links in their construction in terms of quality or durability.
A mattress needs to adapt to your body and take on the shape of your sleeping profile so this is not just normal but necessary for all mattresses … not just latex. Some parts of your body need to sink in more than others or you would have the equivalent of sleeping on the floor (which doesn’t “dip” at all). The key is that each part of your body sinks in “enough” so that your spine is in its neutral alignment and your muscles can completely relax and “let go” so there is no muscle tension from your muscles trying to keep you in alignment instead of the mattress. You can read more about this in post #6 here.
[quote]Ive come across two diagrams :
This one has a graphic of a woman lying on her side, showing proper alignment, but there is also a dip in the latex where parts of her body mold into the mattress.
www.cozypure.com/latex-mattresses/pure-p...th-5-zone-latex-core
Then, i found this graphic on this site that seemed to show that proper alignment would not cause a dip where the poor alignment would.
sleeplikeabear.com/files/2689726/uploade...e_firmness_guide.jpg[/quote]
The second diagram is more of a schematic that shows some general information about what can happen to the spine if a mattress is either too soft or too firm. It doesn’t really reflect what sleeping on a mattress actually looks like as accurately as the picture on the cozy pure site (although this is also a little bit “idealized”).
I wouldn’t worry as much about how much each area of your body may be sinking in as much as your actual spinal alignment and whether your muscles can “let go” and relax in all your sleeping positions.
In general adding a thinner less resilient layer can reduce the “feel” of the resilience of the latex yes. This is one of the reasons that different mattresses use different quilting layers over latex (or in some cases no quilting layers at all). There is more about this in post #12 here.
The key here is that the topper or the quilting layer aren’t so thick that they affect PPP more than just the “feel” of the mattress.
4 lb memory foam would generally be less durable than latex (or higher density memory foam) yes although if you sit on the edge of your mattress it wouldn’t affect where you sleep as much and there are also other factors involved in the durability of a mattress and its useful comfort life relative to each person (see post #4 here). The bigger issue than actual impressions is foam softening (or what you could call virtual impressions that aren’t visible) and if you are in a higher weight range (in the range of 200 lbs or so or higher) then this is something that I would factor in to your personal value equation in combination with your conversations with a knowledgeable and experienced manufacturer yes.
Phoenix