Hi yOnKinaToR,
I have laid on both 19 ILD and 24 ILD on the same lower layers and I can tell a difference. While the difference is not huge, for me at least it is noticeable.
Having said that … this was on the same ILD and thickness of base layers so the only difference in the mattress was the top 3" layer. All the layers in the mattress interact together and because the SleepEz would have a softer middle layer … this will affect the feel of the comfort layer (make it softer) vs a 40 ILD base layer. In addition to this … the Jamison has some foam and fiber in the quilting layer which would work the other way around and make it softer than lying on the latex or the same ILD alone.
So overall … there are some differences between the two mattresses that are more complex to assess than would meet the eye. Since Shawn and/or Jeremy are the experts in their own mattresses … I would talk with him to ask their recommendations. He will probably suggest that you start with the regular “soft” (22-24 ILD) but I believe he can also custom order 19 ILD if it turns out that you need or prefer it and want to exchange the 22-24 ILD for something softer on one or both sides.
Post #2 here talks about split layering and while you would of course feel the difference between the sides (which is the reason for the split in the first place), I don’t think I’ve known or heard of anyone who can feel the split itself with the wool quilted cover.
You’ve probably seen this but there are a several options in the Charleston area in post #2 here which may be worth a phone call and perhaps a visit.
Phoenix