Hi DMN84,
I don’t have any information about your body type or sleeping style but even if I did there is no formula that can accurately predict how a mattress will feel and perform for a specific individual.
It’s always a good idea to do some good local testing on mattresses where you know layering inside the mattress because this can provide you with a reference point about the type of layering that may work well for your body type, sleeping style, and personal preferences.
It’s also very important to make sure you are only dealing with reputable suppliers when it comes to buying your own layers because there are some who will sell you something that is not what they are advertising and “cheap” can often become expensive either in terms of how the mattress works or the cost of replacing layers that don’t work the way you expected. some of the better sources for individual components that I’m aware of are in post #4 here.
As a very general comment that may or may not be applicable to you … your base layer seems to be quite soft for a base layer.
Phoenix