Hi MichaelJBrooker,
Congratulations on your new mattress building adventure! As an overall sort of guidance. the first place I would start is by reading option 3 in post #15 here and the posts it links to (and option #1 and #2 as well) so that you have more realistic expectations and that you are comfortable with the learning curve, uncertainty, trial and error, or in some cases the higher costs that may be involved in the DIY process. While it can certainly be a rewarding project … the best approach to a DIY mattress is a “spirit of adventure” where what you learn and the satisfaction that comes from the process itself is more important than any cost savings you may realize (which may or may not happen).
Using multiple layers would have more options for fine tuning though both before and after a purchase because for example a comfort layer with a 2" soft over a 2"medium layer would generally be a little softer than a single 3" medium layer. You would also have the option to rearrange the layers to medium over the soft, or even have the option to replace one of the layers over time to customize the feel further. The main advantage of having more layers in other words is that for those who need it can provide more options to customize the layer combinations either before a purchase or by rearranging or exchanging layers after a purchase. While this is attractive to some people … it can also add some complexity that may not be necessary or may not justify any extra costs involved in having more layers for others. It all depends upon your tolerance for experimentation.
The companies you mentioned do not produce any latex, but are either distributors or finished product manufacturers. I would consider almost all latex you’re likely to encounter to be a good quality and durable material.
Latex Mattress Factory, Mattresses.net and mattresstopper.com are all members of this site which means that I think very highly of them and that I believe that they compete well with the best in the industry in terms of their quality, value, service, knowledge, and transparency. They are extremely knowledgeable about latex and different configurations, and I would not hesitate to recommend them for your consideration. For a configurable system, both Latex Mattress Factory and mattresses.net can be good sources for guidance in overall comfort and how different ILDs of various types of latex you might be considering will tend to interact with each other. When designing your own mattress, when you’re not attempting to replicate a specific configuration that you’ve liked and have been able to personally test, then the next piece of advice I offer to phone and obtain the guidance from an experienced mattress designer who has a history of building the type of product you’re attempting to create.
The type of encasement you choose to use will also impact the overall comfort of the product, along with protecting your latex layers from mechanical stresses, UV and oxidation. Some people prefer very simple cotton encasements, some people more flexible stretch knits, while others prefer cotton quilted to wool for the unique comfort and protection that wool offers. It really does come down to a personal choice.
Phoenix