i know Phoenix you already told me that you like “not more than 2 inches of memory foam” to go under the latex, and that you like a latex surface.
i also prefer the feel of latex surface - it feels incredibly soft and pillowy to the touch ( 14 ILD that is ) and makes memory foam feel like clay by comparison - but now that i think about it we’re not after showroom feel here, but good night sleep. once you spend a few minutes in bed it’s not an issue of hand feel any more but purely of pressure reduction which memory foam does at least as well as latex. so if i will use memory foam at all then most likely i will put it ABOVE latex and below a wool ( or similar ) mattress pad.
i also saw recommendations online for how thick a memory foam needs to be to do its thing ( pressure point reduction ) but if we’re using latex for pressure reduction already then we’re not using memory foam for that - we’re using it ONLY to arrest small unwanted movements that may prevent your sleep from being as deep as it could be.
now the problem is this - Venus memory foam is expensive as hell and tops out at 2" layer. while Sensus is better priced but is not very breathable - and a thick layer of foam with poor breathability right next to your body is precisely what we don’t need. Aerus
so the question is - how thick will a memory foam need to be to make a real difference in terms of helping you to stay motionless ? not talking about completely making all movement impossible like a tempurpedic - but merely making a significant difference ? just looking for an order of magnitude estimate here.
1" of Venus foam is already a lot of money - would the effect be even noticeable ?
There are no definitive answers to your question and like so many other mattress design questions the only answer is “it depends”. Every layer of a mattress affects every other layer and there are too many other variables such as body type, sleeping positions, and individual perceptions involved to give any kind of meaningful answer based on “theory”. You will need to test different combinations in person so that any answer is relative to your own needs, preferences and perceptions. When you find a mattress that feels and performs the way you want … then you could use this as a model.
One person’s answer may be very different from another’s and only your own criteria are important when you are designing your own. There are no “theoretical” shortcuts that can replace your personal testing or trial and error that will give you enough experience to be able to predict or answer these types of questions in terms of your own personal experience.
Online comments that say things like “a mattress should always have 2” of memory foam" or similar comments generally are much too simplistic to have any real meaning.
Unfortunately politicians don’t tend to tell the truth … or at least only the part of it that suits them. What makes them successful is that people often look for others to provide them with answers or do their thinking for them when they need to discover the answers for themselves. Guidance is one thing … providing you with answers that don’t exist is another completely. What you see as 'hedging" is really the only accurate answer to your questions … even though most people much prefer the “easy” answers that are less time consuming and doesn’t involve their own personal time and testing. Unfortunately only your own personal testing can answer your questions and “theory” just isn’t a reliable way to build a mattress.
You have chosen the most difficult (and possibly costly) way possible to find (or build) your “perfect” mattress and there are no shortcuts that will take the place of your own personal experience and the learning curve it will involve. People that have been building mattresses for decades are still going through their learning curve and will be the first to tell you that you need to “feel” the answers you are looking for for yourself. Nobody can predict what someone else will feel on a mattress in the absence of their own feedback and experience. All you have to do is read the forum and you will quickly discover that in the world of mattresses what is one way for one person can be very different for another.
If you are looking for easy answers that replace your own experience and personal testing … then the answers you receive here will be disappointing and will only be more of the same. I’m happy to point you to information that will give you some insights that may help you (even though you have made comments that they are too in depth for you) but sometimes you just need to go through your own learning curve and find the specific answers that apply to you that nobody else can provide for you.