Hi Sleepy1,
For you 2 layers would probably be enough to provide the pressure relief and alignment you needed (even if it didn’t “feel” as good as 3 layers). For your partner though “theory” says that 3 layers would be much better. You could test this for yourself though by testing a 2 layer Savvy Rest or even a 6" latex mattress that may be available locally because your own testing will be more accurate than any “theory at a distance”. My tendency though would be to suggest that you would be happier with a 3 layer mattress.
Unless you had specific preferences or compelling reasons to choose otherwise … in most cases and for most people I would say the answer is no and I think that they would also suggest the same thing. You can read more about some of the different types of latex and blends available and which may be better “value” for most people in post #6 here.
I would remember that primary support doesn’t come from the top layer which is mostly about pressure relief but from the deeper layers which are the ones that “stop” the heavier parts of the body from sinking down too far. The reason that Talalay often provides better pressure relief for some people isn’t because it is inherently more conforming but because it is generally available in softer ILD’s than Dunlop. This really is a matter of preference and not a “better worse” comparison. The top layer does provide secondary support by filling in the gaps in the sleeping profile and helping to support the more recessed areas of the body which require much lower levels of “support”.
If both of you have broad shoulders then you may need a comfort layer that is a little softer to allow" the shoulders to sink in far enough if you sleep on your sides and this may be more important for your lighter weight than for your partner who ill sink in deeper with higher ILD’s. I would test specifically for this in your local testing along the lines of this article. If you don’t sleep on your side … then a firmer comfort layer would probably be more appropriate given the circumstances and preferences you’ve mentioned. Your own experience will be the most accurate indicator though (either with local testing or your experience with the mattress after you sleep on it) and since a comfort exchange is capped at a $30 cost … I would do my best to make the best possible choice initially in consultation with Shawn or Jeremy but there would be little worry or cost if you do need to exchange a layer.
I would also strongly suggest adding some slats to this or some type of firm more evenly supportive base such as a bunkie board (see here) or even this bed rug. 5" gaps are too far apart for a latex mattress IMO. You will also need support to the floor under the center beam and 4 legs won’t be enough if you are buying a queen or a king.
Phoenix