Hi Ho,
While it’s not really possible to “diagnose” mattress comfort issues on a forum because there are too many unique unknowns and variables involved that can affect how each person sleeps on a mattress in terms of PPP (Posture and alignment, Pressure relief, and 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.
There is also 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” and “pressure relief” and “feel”.
These posts are the “tools” that can help with the analysis, detective work, or trial and error that may be necessary to help you learn your body’s language and “translate” what your body is trying to tell you so you can make the types of changes that have the best chance of reducing or eliminating any “symptoms” you are experiencing.
The only actual “symptom” I can see in your comments is your shoulder numbness which generally indicates either that you could benefit from a softer zone under your shoulders (and this could be why the tension adjustable slats were working for you previously) or it could also point to a pillow issue as well.
You also mentioned that the mattress “felt like” it was too firm but comments that only include the “sensations” you are experiencing and include terms like “felt like” or that talk about how much you are sinking in but don’t describe the specific symptoms you are experiencing are very subjective (see post #6 here) and it may also just be a matter of getting used to the mattress without the Euro Slat Foundation (see post #3 here).
In very general terms if a mattress “feels” too firm but there are no specific symptoms connected to the “feeling” then it may require some trial and error with rearranging or exchanging layers to soften up the mattress (moving firmer layers down or softer layers up will generally soften up the mattress and replacing a firmer layer with a softer one will also soften up the mattress) but this will also depend on whether you are talking about “pressure relief” firmness (which may involve softening up the upper layers) or “support” firmness (which may involve the deeper layers) and if the “feeling” of the mattress being too firm is connected to a specific area of your body it may also involve rearranging or exchanging some of the zones or moving the zoned layer up or down.
Because all of this can become very complex … my “best” suggestion would be a more detailed conversation on the phone with Flobeds about your experiences and the types of changes that may be helpful so you can take advantage of their knowledge and experience with other customers that are in similar circumstances or have similar experiences to yours. They will be more familiar with their mattresses and the options they have available and the types of changes that may be helpful than anyone else (including me) and it’s much better to deal with these types of “fine tuning” changes with a more interactive voice conversation than through written “conversations” that may take many hours of back and forth communications to even get to the level of clarity about your experiences that would be necessary to even begin to make any specific suggestions. Voice communications can accomplish in minutes what written communications can often talk many hours or days of back and forth questions, comments, and replies to accomplish.
Phoenix