Hi Thegandork,
I wouldn’t try to configure the layers at all since most people don’t have the knowledge or experience to design their own mattress.
When you can’t test a mattress in person … the most effective way to choose the layering that has the highest chance of success for you would be a more detailed conversation with SleepEz who will know more about “matching” their mattresses to your body type, sleeping style, and preferences and your local experiences than anyone else (see mattress firmness/comfort levels in post #2 here).
Just in case you haven’t seen it … the better options and possibilities I’m aware of in the Boise/Nampa, ID area are listed in post #2 here which may also give you the chance to test a few latex mattresses which may provide some useful reference points when you talk with SleepEZ.
Phoenix