Hi sheep123,
It sounds like the toppers you are using aren’t the most suitable combination for you (and your mattress pad may be interfering with the response of the latex as well).
If your mattress is sagging when you have it on the floor though then I would contact European Sleepworks because you may have a warranty issue.
It sounds like you are certainly sensitive to some very soft materials but as you know that’s not unusual for those with fibromyalgia.
Each person is also unique when it comes to the type of material that they tend to do best with or the type of mattresses or materials they tend to prefer and not everyone likes the higher resilience or “feel” of latex or the slow response of “feel” or memory foam.
Since you have eliminated two of the three types of foam then it would make sense to me that a polyfoam comfort layer would be well worth trying.
Most of the “feel” of a mattress when you first lie on it comes from the upper layers but the deeper layers will also contribute to how a mattress feels as well. There are hundreds of different types of innersprings with different firmness levels that are used in combination with hundreds of different combinations of materials on top of them so there isn’t a single “feel” for innerspring mattresses that you can use to compare them to other mattresses. The same is true for mattresses that use polyfoam support cores so the only way to know how two mattresses compare and the differences you would feel between them would be based on your own personal experience but in very general terms an innerspring support core will have more “bounce” and “springiness” than polyfoam which will be less “lively” and responsive.
It seems that you’ve already read my comments about the new Tuft & Needle design in this topic so you have some basic information to go by. I would also suggest a conversation with them on the phone so you can describe your circumstances and experiences with other mattresses you have slept on so they can let you know whether they believe their mattress would be a good choice for you.
Your own personal experience will be the only reliable way to know whether an online purchase that you can’t test in person will work well for you but if based on your conversation you believe that it would be a reasonable choice then there would be very little risk in trying it because if for any reason it doesn’t work out as well as you hope then they have a great return policy.
The previous version of their mattress also used good quality and durable polyfoam and the biggest difference in their new material would be in it’s contouring, feel, and response although with its higher density it would also be a little more durable as well.
Phoenix