Hi Diane37,
For most people edge support isn’t an issue with foam mattresses (memory foam or latex) but some people who do sleep with their body on the very edge of the mattress (or partly off the mattress) or who want very firm edges for sitting may well prefer a firmer edge. Post #33 here and post #2 here has more about the pros and cons of edge support. The firmness of the latex core and the thickness and softness of the latex comfort layers relative to your weight along with the normal break in of the mattress where the covers stretch a bit and the latex softens a bit will also make a difference. I know that I certainly don’t feel like I am “rolling off” my latex mattress when I sleep on the edge (which I sometimes do) but other people may have different perceptions from me. I have a two sided mattress which by most people’s standards would be very soft and it has a 28 ILD middle support layer and 3" of 22 ILD on each side and I am 6’ 5" and my DH is 5’ 7" and about 130 lbs. These types of issues are all very subjective and individual and while they are not normally a concern with a latex mattress … you can always test a local mattress that is similar to see if this would be an issue for you.
Post #2 here has more of the “theory” behind different designs but these are more generic and there are too many variables and unknowns to use them or make suggestions on an individual basis based on “theory at a distance” without a reference point of mattresses you have tested. Outside of your own personal testing on similar mattresses (if there are any available locally), the best way to make your design choice is the guidance of a manufacturer or retailer that you are buying from that has the experience and knowledge to help you make the best possible choices based on the averages of their customers that have similar body types, sleeping styles, and preferences as you. All good manufacturers (and Arizona Premium is certainly one of these) will make suggestions based on the information you provide when you talk with them on the phone that they believe have the best odds of success for your specific circumstances. If you ask 10 people on a forum you may get 10 different answers because most people only know what works for them and not for other people. A manufacturer will know which of their options will tend to work for “most” people in your circumstances as long as you provide them with enough specific information on a phone call.
Softer layers will feel firmer to people who are lighter than they will to someone who is heavier because they don’t have the weight to sink in as much.
A 100% natural talalay layer on top of your mattress in the lowest ILD’s will generally be less durable than a blend although all types of latex are more durable than other materials in the same softness level. Once you are in the mid 20’s or so then the difference in durability would probably even out. This may also depend on the manufacturer because Latex International says that their all natural is less durable but Radium says that both types should be equivalent even in lower ILD’s because they use a different curing paste that creates a more dense product in their all natural latex in lower ILD’s. A good manufacturer such as Ken will have the long term experience to be able to tell you how they compare in “real life” instead of just based on theory or the claims of a particular manufacturer. A “soft” core in your support layer is still “medium” (it’s only “soft” relative to other support cores) and only the upper layer would actually be soft but 22 ILD is close to the point where they would even out if there was a difference or the difference would be small (or perhaps non existent with Radium).
I would keep in mind though that all latex is a durable material regardless of its type and these are only comparisons relative to other types of latex not to other materials. The benefit of all natural is that it is more resilient and has a higher compression modulus so while it may not feel quite as “soft” as blended in the same ILD, it is more supportive (gets firmer faster as you sink in more).
Phoenix