Hi onethinline,
While I know it’s not quite the way you want it yet … you certainly made a high quality and very durable choice … and congratulations on your new mattress 
I would keep in mind that there will be a break in and adjustment period for any new mattress or sleeping system as the mattress loses any of it’s “false firmness” and the cover stretches and loosens a little and the materials settle and your body gets used to a sleeping surface that is different from what it is used to (see post #3 here and post #2 here). This would typically be a few weeks but it can be shorter or longer depending on the specifics of the person and the mattress (higher density materials can take longer) and it can be surprising to many people how much their sleeping experience can change over the course of the first month or so. I would generally suggest sleeping on any new mattress for a few weeks at a minimum (preferably a month or so) whenever possible before deciding on whether it’s a good “match” in terms of comfort, firmness, and PPP and/or deciding to make any changes or additions to your mattress.
As they mentioned … if the pocket coil is thicker than their previous model then it can pre compress the latex layers so it certainly wouldn’t be unusual that it would feel firmer. Unzipping the cover should also make “some” difference in terms of softness although it seems that it may not be enough (although the break in period may be partly responsible for that as well).
[quote]The owners (a father and son) have each offered a different resolution, and here’s where I’m torn. The first suggestion is to swap the coils out for the type they used previously, which are an inch shorter and will allow the middle latex layer the room it’s supposed to have in the cover. The second suggestion is to use two covers to convert the coils and first layer into the other hybrid mattress, then cover the top extra-soft layer making it a topper: this basically reproduces the jerry-rigged setup I tried and liked in the store.
Obviously, the latter seems like the surer bet, but I would prefer one integrated cover to make a single-piece mattress. I’m also still wondering whether somehow the top layer isn’t actually extra soft, since even after unzipping and de-compressing the middle layer, I’m still getting pressure on my shoulder throughout the night.
The set-up I tried in the store really did feel good so I don’t want to give up. If I have them switch to the shorter coils, I’m taking some risk in how it will feel, but I like the idea of switching to the design intended for the integrated cover. On the other hand, the mattress-plus-topper configuration should be exactly what I liked, but feels like a compromise somehow. Any thoughts? [/quote]
Both options would likely result in a softer “feel” but if I was in your shoes I would tend to lean towards the mattress/topper combination. I certainly wouldn’t consider this to be a “compromise” at all and there are many people that choose to sleep on a mattress/topper combination and prefer it vs a mattress that contains all the same layers inside the mattress cover because a separate topper can “act” a little more independently and “feel” a little softer outside a cover than it will by having the same layer inside the cover (see posts #3 and #4 here and the first page of posts in this topic). This could also be part of the reason for the difference you feel as well and it would make sense to use the same design for your “sleeping system” as you tested and preferred in the showroom.
Phoenix