Hi dsw61,
Latex Green 100% natural Dunlop that has a density of about 80 kg/m3 would be a medium firm layer and would have an ILD range of somewhere between 28 - 33 ILD (see here). The ILD would also vary from the top to the bottom and and at different points across the surface as well so a 28 ILD layer and a 31 ILD layer may both be the same firmness anyway. Latex doesn’t come in exact ILD’s (only ranges) and I would also agree that most people wouldn’t feel any difference between 2 layers that are only 3 ILD apart even if it was the top layer (which is the one you would tend to “feel” the most) and in deeper layers it would be even less likely that you would feel any difference.
Phoenix