Hi deuxcv,
Welcome to the Mattress Forum! 
You’re welcome!
I would keep in mind that “comfort” is completely subjective and a mattress that is “comfortable” for one person may be uncomfortable for someone else. While other people’s comments about the knowledge and service of a particular business can certainly be very helpful … You are the only one that can feel what you feel on a mattress and I would be cautious about using anyone else’s suggestions, experiences or reviews on a specific mattress (either positive or negative) or review sites in general as a reliable source of information or guidance about how you will feel on the same mattress or how suitable or how durable a mattress may be for you. In many if not most cases they can be more misleading than helpful because a mattress that would be a perfect choice for one person or even a larger group of people in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) may be completely unsuitable for someone else to sleep on (even if they are in a similar weight range. In other words … the “bottom line” is that the only reliable way to know whether any specific mattress is a good “match” for you in terms of comfort, firmness, and PPP is based on your own careful testing (hopefully using the testing guidelines in the tutorial) or your own personal experience when you sleep on it, regardless of how anyone else may “rate” the same mattress (which you already alluded to in the middle of your post).
[quote]below are the configs i tried in order of firmness. #2 and #3 are the two i chose (left and right), since i couldn’t make up my mind in the store.
- -naturepedic “plush” – plush coils / soft latex. this was too soft for my liking.
- -my own “medium” – plush coils / med latex. this seemed good in store, but might feel a little soft in practice.
- -my own “medium+” – plush coils / firm latex. this was noticeably softer than naturepedic’s “cushion firm”. but in practice maybe feels too firm. wondering if it/I just needs some break-in time to soften up a bit.
-naturepedic “cushion firm” -firm coils / soft latex. this felt too firm in the store.
i am really fascinated by the effect of the spring’s stiffness on the feel of the soft latex in #4[/quote]
Did you try out a firm spring with the medium latex on top? I think what you really may be experiencing in #4 isn’t the firm springs “stiffening up” the feel of the soft latex, but in actuality the soft latex allowing you to “sink in” and “feel” more of the firm springs. I’m guessing you can’t change out the spring unit. If you could, you might be surprised that by placing a bit of a firmer latex on top of the firm unit that it actually could be a more comfortable “firm” feel than #4.
There is more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel” that may be useful in understanding their relationship.
How long have you had the mattress?
i[quote] can’t change the actual stiffness, but here are some of my ideas and welcome your feedback or additional ideas.
put a thin layer of something between the coils and latex. what comes to mind is a ⅛" to ¼" of wool felt. this wouldn’t be enough to significantly compress the springs, but might lessen the spring’s reaction to pressure, thus in my mind might make the overall firmness a little stiffer.[/quote]
This might actually stiffen up the transition from the upper comfort layer to the spring unit, resulting in a bit more of a delineated/abrupt transition from comfort layer to spring unit. I can’t speak to how this might feel as there are quite a few variables with what you would place between the foam and the spring unit.
or[quote]- adding maybe 1" of some sort of foam to the bottom (underneath the coils) to partially compress the springs. I think berkeley ergonomics and/or europpean sleep works in berkeley do this in some of their offerings. my thinking is that if the springs are partially compressed, they will be a little stiffer. i thinnnk there would be enough room in the casing to achieve this, but this might also have other unforeseen consequences if everything in the casing is under greater compression.[/quote]
Since you can’t change out the spring unit, this might be a more viable option. I wouldn’t worry too much about the covering of the EOS not being able to handle the stress of an extra 1" of padding inside, as it is a durable covering. Depending upon the progressiveness of the spring unit, this “precompression” could firm up the spring unit a bit. Realize that it will also “precompress” the foam a bit as well, as you’ll be putting the entire interior contents under a bit of additional stress. Adding this layer of foam would be different from placing the innerspring unit in more compact fabric encasements, where only the spring unit would be compressed. I’d be interested in learning about how this turned out if you decide to go this route. You’d want to make sure that you used a foam with a higher ILD and good density.
You’re starting to enter into a bit of a partial DIY area, so the experimentation could be a fun adventure, especially if you’re not spending too much money on additional componentry.
I’ll be interested in learning what you decide to do.
Phoenix