Hi rickwell,
Post #15 here has more about glued vs loose layers and which may be preferable in different types of constructions.
ILD is only one of the variables that can lead to a mattress that is much different from another. Some others include the type of latex (ILD’s don’t necessarily “match” between different types of latex) and the thickness of each individual layer as well as the type of cover and the quilting in the cover. All of these will have a combined effect on the feel and performance of the mattress.
You can read a little more about “matching” one mattress to another in post #9 here. Each difference in the design, type of materials and components (including the cover) and in the firmness of each layer can make a difference in how the mattresses compare. You can read a little more about the difference between natural and blended talalay in post #2 here but in general 100% natural Talalay is a denser material so it will be firmer with deeper compression than blended talalay although if the ILD is the same they will be very similar if each layer is compressed exactly 25% where ILD is measured.
Once you know the exact design, layer thicknesses, ILD’s, and types of latex in a mattress and know the type of cover it uses then a phone call to SleepEz would give you their best guess about which of their options may come closest. None of their mattresses have a 4" top layer so that would mean that approximating the design which would involve some “translation” and guesswork. The design of the SleepEz is closer to the Savvy Rest so it may be a little easier to approximate one of the Savvy Rest layer combinations than the Sensation.
Phoenix