Hi Goat,
Post #2 here should be helpful 
With a suitable quilted cover (or with a solid layer of latex or other material above the split layers in the case of an unquilted stretch cover) you will feel the transition from one firmness level to the other (which is the reason for the split layering) but not the “split” itself.
Latex layers are quite heavy and “sticky” and don’t tend to shift on top of each other inside a suitable tight fitting mattress cover but if for some reason this were to happen (for example if you were moving the mattress and turned it on its side) it’s also easy to unzip the cover and move them (with a “waving” motion) back into place
Phoenix