Hi B Feelgood,
If you aren’t using a specific all latex mattress that you have tested and confirmed is a good “match” for you as a reference point then I would take a “bottom up” approach rather than a “top down” approach and decide on your base layer first (or in a three layer mattress the bottom two layers … making sure that if anything it would be a little on the “too firm” side) and then choose the thickness and firmness of the layer or layers on top of it according to your sleeping experience on your previous choices (post #2 here and the topper guidelines it links to may also be helpful).
Once you have finalized the thickness and firmness of your layering then you can choose the type of cover you prefer in a suitable thickness.
I would certainly agree that 6" of 19 ILD Talalay would be too thick/soft for most people.
Phoenix