Hi pastacats,
The first place to start is the tutorial post here which has all the basic information, steps, and guidelines that can help you make the best possible choices.
I would also read post #15 here and the posts it links to before going in the direction of a DIY mattress and I personally would look at the online manufacturers who are members here who make a “kit” mattress where you can put your own layers together inside a high quality cover and where you have the ability to exchange layers if you make the wrong choices.
It may also be worthwhile looking at some of your local options because there is often some great options available locally. If you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of.
[quote]Another “DIY” option I came across was to stack latex toppers to create a mattress… this appears to be much less expensive than other options. For example, one could buy two 3" king toppers from this company (www.rockymountainmattress.com/natural-la…-dunlop-medium-firm/) for $488.99 each, have them shipped free, and end up with a king latex mattress for $977.98.
Any potential disadvantages to this? [/quote]
The “risk” with any mattress that you haven’t tried in person and where you are putting “random” layers together (whether they are individual layers or covered toppers) is that you make the wrong firmness choices and they won’t be the ideal firmness choices or a good match for you in terms of PPP. 6" may also be on the thin side for many people and most (but not all) people would be do best with something in the range of 8" to 9" (see post #14 here). If you have tested a local mattress that has the same two layers as the ones you are considering (in terms of thickness, type of latex, and density/firmness level) with a similar cover (which will also have a significant effect on how the mattress feels and performs) then it would be a less risky choice.
I would also make sure you have experienced the difference between Dunlop and Talalay latex because they have a different “feel” and many people prefer one over the other although neither oneis “better” than the other. You can read more about the different types and blends of latex in post #6 here.
Phoenix