Wife and I are sleeping on a king DIY latex mattress using 3 talalay layers purchased from mattress247 .
The original configuration was (top to bottom) S-M-F, but after a month or so I found that to be not supportive enough, so I switched it to S-F-M. The support is much better, and if feels more like a traditional mattress as far as sitting and changing position. The slight downside is it is a tad bit too firm, but livable (or so I thought) as we have been sleeping on it for about 10 months.
A couple of days ago I put a king sized foam “mattress elevator” under the mattress to help with reflux issues. It’s a 5 inch wedge that gradually tapers down to the foot of the mattress. I am quite pleased with the results, in fact I think it makes the bed more comfortable, perhaps because it redistributes body weight somehow. This is despite the fact that it seems to firm up the mattress a bit more.
Sadly, the wife does not share my enthusiasm for the change, and says it makes the mattress too firm, and took the opportunity to say she’s always thought the mattress was too hard. I told her we can always try a different laying configuration, and here’s where I finally get to my question,and the reason for my question.
The ability to change the configuration of the layers is wonderful, but repeatedly moving, handling and orienting three king size latex layers is quite a task. I’d rather not go back to S-M-F if possible, but I am curious if M-S-F would generally be softer OR firmer than the current S-F-M configuration. I understand that our personal experience is the main factor, but if I know that such a change would generally be firmer than what we currently sleep on, I might end up just going back to S-M-F.
I would agree that it’s not a good idea to constantly rearrange layers because no matter which combination of layers you use if you are like the vast majority of people you will have times when you you don’t sleep as well on any mattress that you normally sleep well on most of the time and it can be too tempting to change layers each time you have a period of time when you aren’t sleeping as well even though in most cases it would normally be related to your daily activities or circumstances and to normal changes and rhythms in your body more than to the mattress itself. I would generally stick with a combination that you sleep well on “most of the time” because if you make too many changes you can get caught in a cycle where your body is constantly trying to adjust and nothing feels comfortable any longer.
I would also look at any actual physical symptoms you are experiencing on a mattress to decide whether to make any changes to your layering rather than going by the “feel” of a mattress which is very subjective and not nearly as important to how well you sleep as your spinal alignment (which is the single most important factor in how well you sleep and how well your body rests and recovers over the course of a night) and pressure relief (which is the next most important factor in how well you sleep).
While it’s not possible to “diagnose” mattress comfort issues on a forum with any certainty because they can be very complex and there are too many unique unknowns, variables, and complexities involved that can affect how each person sleeps on a mattress in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) or any “symptoms” they experience … there is more about the most common symptoms that people may experience when they sleep on a mattress and the most likely (although not the only) reasons for them in post #2 here that can help you decide on the type of layer changes that would have the best chance of success.
“Support” is also often misunderstood because the goal of a “supportive” mattress is to keep the spine and joints in neutral alignment and this requires the type of contouring support that allows some parts of the body to sink in more (softer) and some parts of the body to sink in less (firmer) and this will vary on an individual basis based on body type and sleeping style. 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 and in post #4 here that may also be helpful in clarifying the difference between “support/alignment” and “comfort/pressure relief” and “feel” and how they interact together.
In other words … if you aren’t experiencing any actual specific symptoms on a mattress such as lower back pain or discomfort then the mattress is probably a suitable configuration for you and I wouldn’t use the “feel” of the mattress to decide on the most appropriate layering combination. Your body will tell you whether a specific combination of layers is suitable for you based on actual symptoms of pain or discomfort you experience much more than your preferences about how it “feels” which is much less important.
On to your actual question …
Different people can have very different perceptions of firmness and softness compared to others and a mattress that feels firm for one person can feel like “medium” for someone else or even “soft” for someone else (or vice versa) depending on their body type, sleeping style, physiology, their frame of reference based on what they are used to, and their individual sensitivity and perceptions. There are also different types of firmness and softness that different people may be sensitive to that can affect how they “rate” a mattress as well (see post #15 here) so different people can also have very different opinions on how two mattresses compare in terms of firmness. This is all relative and very subjective and is as much an art as a science.
M/S/F would have a firmer top layer so it would be less pressure relieving and would provide a little firmer secondary support but the deeper layers that provide the primary support would be softer than a S/F/M combination so it will be firmer in some ways (and will probably “feel” firmer since most people will “feel” the firmness of the upper layers more than the deeper layers) and softer in terms of primary support (which you may feel more when you wake up in the morning than when you go to sleep at night).
Unfortunately the only way to know whether you will sleep better on any combination will be based on your own personal experience over the course of a few weeks. I would also try any new combination for more than just a few days because it can take longer than that for your body to adjust to any change and your experience over the course of just a few days can be an anomaly or the result of the change itself and may not identify any meaningful patterns in your experience.
Because I can’t feel what you feel on a mattress and there are too many unknowns and variables involved for me to be able to predict how well you will sleep on any mattress design based on specs (either yours or a mattress) … the only way that I would be able to guess whether a change in layering may be worthwhile trying would be based on knowing the actual physical symptoms you are experiencing and how your symptoms actually change (either for the better or for the worse) with each combination you try relative to the others because it’s the actual changes in your experience and symptoms that are the only real reference points that can help identify any layering combinations that may have the best chance of success.
If you have split layers then you can also configure each side of the mattress differently and if you don’t and you think it’s necessary you can also cut one or more of the layers in half using an electric knife but I would hold off on this unless you find that both of you can’t agree on the same combination.