Hi Siggy,
As I mentioned in my previous reply … the most common (but not the only) cause for lower back pain is either comfort layers (including toppers) that are too thick and/or soft or a support core that is too soft so it sounds like your topper may be a little thicker than you need and you may have “jumped over” the firmness that is the most suitable “match” for you in terms of comfort, firmness, and PPP and gone from a mattress that is too firm for you to a mattress/topper combination that is too soft to maintain good spinal alignment over the course of the night.
I would also keep in mind that the neck issues you originally had with the medium mattress may have been a pillow issue as much as a mattress issue.
With your wife’s lower weight it’s also possible that her shoulder issues may have been a pillow issue as well although based on your comments and feedback the odds are higher that for her it could be a firmness issue with the mattress as well (based on “averages” … lower weight ranges will tend to do better on softer mattresses than higher weight ranges).
It’s not unusual at all for a couple to have different needs and preferences and here is more information in the first part of post #2 here about some of the different ways that can be used to accommodate a couple that have very different body types or sleeping styles or different needs and preferences in a mattress.
While this is a possibility … it would result in one side being thicker than the other and the ridge in the middle would likely be very noticeable. If you were to take this approach it would probably make more sense to use a firmer topper on one side than the other (with the same thickness) so that the entire sleeping surface is more even.
You can read more about the type and quality/durability of the materials in the Helix along with many of the other simplified choice mattresses in post #2 here in the simplified choice topic. Post #1 in the same topic would also be well worth reading. A forum search on “Helix” (you can just click the link) will bring up more comments and feedback about them as well.
The Helix mattress includes 2" of 1.8 lb polyfoam in the comfort layers which is the minimum polyfoam density I would suggest for those that are in more average weight ranges. They also use 1.5 lb polyfoam in the base layers of the mattress and while the deeper layers will have less effect on the durability and useful life of a mattress … it’s still a little lower than I would normally like to see in a mattress in this budget range. The deeper layers can still have “some” effect on the durability and useful life of the mattress but the effect would be more for those that are in higher weight ranges and/or that tend to compress the deeper layers of the mattress more than those that are in lighter weight ranges.
The microcoils themselves are a good quality and durable component and there is more about microcoils that are used in comfort layers in this article and in post #8 here and post #2 here (although how much you will feel the microcoils will depend on the order of the layers).
Assuming that the materials in a mattress you are considering are durable enough for your body type and meet the quality/durability guidelines here relative to your weight range … the choice between different types and combinations of materials and components or different types of mattresses are more of a preference and a budget choice than a “better/worse” choice (see this article). The most reliable way to know which types of materials or mattresses you tend to prefer in more general terms would be based on your own local testing or your own personal experience. when you sleep on it.
Phoenix