Hi feebewitz,
There are only two ways I know of to choose a mattress that is “right” for you in terms of PPP. The first is your own careful and objective testing using the testing guidelines in the tutorial post and the second would be more detailed conversations with an online retailer or manufacturer (see mattress firmness/comfort levels in post #2 here which you may have already read).
If you aren’t confident in your ability to make a suitable choice that is “close enough” with either of these then the options you have available after a purchase to fine tune the mattress or to exchang the mattress or exchange or replace individual layers or the return policy of the retailer or manufacturer you are dealing with (and the costs involved with any of these) would become more important and I would make sure you factor this in as part of your personal value equation.
Dunlop only feels firmer if you are comparing the same ILD and layer thickness to each other and you sink into the material more than 25% of its thickness. Both Dunlop and Talalay come in a wide range of firmness levels so either one can be firmer than the other depending on the specifics of each layer and on the rest of the mattress that it’s part of.
You can read more of my thoughts about Habitat and their return policy in post #3 here and a forum search on Habitat (you can just click this) will bring up more information and feedback about them as well.
I think highly of SleepOnLatex but before you consider designing and building your own mattress and purchasing all the layers separately rather than as a component kit I would read post #15 here and the posts it links to.
Phoenix