Hi lebaryo,
There are links to some of the “theory” in mattress firmness/comfort levels in post #2 here but there are too many unknowns and variables to use these to make specific suggestions for any specific person or use them as anything else but concepts that can be useful guidelines. There is also more in post #2 here about more vs less layers.
[quote]I found the Nature a bit too firm for my liking. The dealer said that the nature uses Latex International latex that’s 10" with a 6" base core that’s 36 ILD, 2" middle core of 28 ILD, with a 2" top core being 21ILD.
I thought that the “Beautiful” model was much more comfortable and absorbed my body a little bit better. The beautiful used a 6" support core with a 36 ILD, a 3" middle core of 24ILD and a 3" top core of 21 ILD.[/quote]
The specs you received are accurate (see post #2 here) and all of the PLB mattresses use good quality materials.
You can read a little more about “matching” one design to another in post #9 here but your testing can certainly provide a good guideline that a manufacturer can help you “translate” to some degree into their own designs and the options they have available. The Beautiful uses more soft latex in the top layers than many manufacturers would be comfortable with.
There are several manufacturers in the area that use a 3x3 design including Foam Sweet Foam and Savvy Rest dealers.
You are doing some good research 
Phoenix