Hi kirstyj21,
Unfortunately this is not an uncommon issue when your mattress has thick layers of rather low quality materials. If these materials soften then they can allow you to go through the top layers and feel much more of the firmer layers below them. Thicker layers of lower quality materials are the main cause of the loss of comfort and support of a mattress. When you are light and curvy then you need a comfort layer that is thick and soft enough to fill in the gaps in your sleeping profile and distribute pressure away from the pressure points and isolate you from the firmness of the support layers. This is the balance between comfort and support that is part of both the art and science of making and choosing a mattress.
Unfortunately if the cause of the issues you are having is due to the softening of thicker comfort layers … then a topper would probably not be the most suitable option. While it could isolate you from the firmness of the support layers and reduce your pressure points … you could easily end up with an alignment issue even though both of the toppers you linked are good quality materials (probably made by either Latexco or by Artilat in Belgium).
That was a confusing thread and she was holding on to some ideas that were simply not correct which caused her a lot of difficultes. I would probably ignore the thread completely as it may be much too complex to follow easily or apply to your circumstances and really be helpful.
I hope you are successful but the odds are low that you will receive a refund and the sad truth is that the same thing would probably have happened at almost any other mainstream store as well. Their argument would be that you tested the mattress and found it suitable and that there is no way for them to know for certain which type of mattress is suitable for a specific customer (and there is some truth to this because each person is different and there is no formula that can predict the needs and preferences of each person). Your mattress appears to have a fairly thick comfort layer and is rated as “plush” (not firm) so “in theory” at least it could have worked well. The problem is that they use materials that will soften too quickly not so much that the mattress is unsuitable when it is new and the second issue is that foam softening and the resultant loss of comfort and/or support isn’t covered by warranty unless the foam actually forms unweighted impressions that are deeper than the warranty exclusion which is not usually the case (you can see more about warranties in post #174 here). I know that this is frustrating to say the least but until consumers insist on knowing the quality/durability of the materials in a mattress there is little hope of significant change in the mainstream industry. I would persist as far as you can but keep your expectations of success realistic.
Pillowtops themselves are not the issue and they can be a useful and valid method of construction. The problem with most pillowtops is the type and quality of the foam in the pillowtop … not the actual pillowtop design. A mattress without a pillowtop can be made just as soft or softer than many pillowtops depending on the materials in the comfort layers and the overall design of the mattress. You can also read more about the many factors that can work together to affect sleeping temperature in post #2 here and softer or less breathable foams or fabrics or materials in or on a mattress that reduce or restrict ventilation or the wicking of moisture and humidity (including some mattress protectors and sheets) can act together to create issues with sleeping temperature.
I would avoid trying to design a mattress based on specs and focus more on the quality, durability, and type of materials you prefer and on how they feel and perform in your testing. Learning how all the mattress specs and designs work together can take years of experience and a great deal of knowledge and a steep learning curve to be successful. Double sided would certainly be more durable than a single sided mattress but there is also less design flexibility than a single sided mattress because the softer comfort layers on the bottom can’t be so thick and soft that they affect support and alignment. Single sided mattresses that use very durable materials (especially in the comfort layers) can also make a good choice … particularly if the design allows you to exchange or replace single layers so if the top layers soften sooner than the deeper layers (which is usually the case) then you can replace just a single layer without replacing the complete mattress. If you prefer more natural materials then a mattress that uses some combination of 100% natural latex, natural fibers, or innersprings would be the most common choice and all of these are durable materials.
The guidelines in post #1 here are the steps I would follow and I would avoid trying to design your mattress based on specs. The specs that are important are the ones that identify the quality and durability of a material so you have a good idea of how long your mattress may last … not the ones that have to do with comfort and support which you can test in person much more effectively. The goal is to focus on PPP (Posture and alignment, Pressure relief, and Personal preferences) based on your personal testing and to make sure that the materials inside the mattress are good quality so they won’t soften or break down too quickly and will maintain their original properties over the longer term.
Not enough meaningful or accurate information can lead to some unfortunate choices but too much information or overthinking your choice can also lead to “paralysis by analysis” and lead to poor choices just as easily. In most cases “finding the experts” that are comfortable talking about the materials in their mattresses and who are focused on educating their customers more than “selling” them using “marketing stories” can be a much more important part of choosing the most suitable mattress than becoming an expert yourself. In the end only each person can feel what they feel on a mattress and the most knowledgeable and experienced salespeople and manufacturers understand that the best they can do is to provide some guidance and education about how to choose, not what to choose, along with accurate information about the pros and cons of each material and design. They also know that once you have all the information you need ten they need to step out of the way because only each person can make the best choice for themselves.
If there are no good local options then I would also consider an online choice but in this case you would be making a choice based on more detailed conversations with a retailer or manufacturer and be using their experience and knowledge of their own mattresses and the “averages” of their customers with a similar body type and sleeping style to make your comfort and support choices. Their knowledge and experience would be particularly important in choosing a mattress that you can’t test beforehand. In this case it can be important to make sure you have good options after a purchase to either exchange layers or return the mattress in case the “averages” that work for most people that is the basis for their suggestions and guidance don’t apply or work well for you.
Phoenix