Hi Mestone,
I certainly understand this because “theory” by itself isn’t particularly meaningful until you also have the personal experience on different types of latex mattress designs to “translate” all the information you read into “real life” experience.
The thickness of a mattress is only one of many factors that can affect how soft or firm it feels to a particular person and it often isn’t the most important factor because the specifics of the design and materials inside the mattress can have a bigger effect than thickness on how soft or firm a mattress feels (see post #4 here). The Nutrition for example has a dominating layering (see post #33 here) that uses a firmer comfort layer over a softer transition layer and to many (but not all) people it would feel firmer than the Nature because the top layer is firmer even though it’s also thicker.
If you let me know your city or zip code I’d be happy to let you know about any of the options or possibilities I’m aware of in your area. Some good reference points based on your own actual experience on different types of latex mattresses can be more important and a more relevant guideline than “theory at a distance” when you are designing your own mattress.
28 ILD comfort layers would certainly be a common choice for side sleepers that are either in higher weight ranges or that prefer slightly firmer comfort layers than some of the softer ILD’s that are available but the only way to know how it would feel to you in combination with the other layers and the type of cover you are considering would be based on your own personal experience.
It’s can also be a good idea to take an incremental “bottom up” approach where you order your base layer and say a 3" 28 ILD layer on top of it and then use your actual experience on these two layers as a reference point to decide on any additional layers or softness you wish to add to your design and then leave the choice of cover until after you have confirmed the combination of layers and the thickness of the mattress that you are happy with.
Phoenix