Hi jd,
It’s unfortunate that the OMI (Organicpedic) Duo isn’t working out for you as well as you’d hoped because it certainly is a high quality mattress.
It seems to me that you are somewhat “stuck” in between two configurations and with your sensitivity and shoulder issues you are probably more sensitive to pressure issues than most. As you already suspect … these are situations where zoning can be an effective solution that can help to “fit” more difficult body types and situations. The challenge is that there is no formula that can predict what will work best so finding an effective solution may take some trial and error.
It also seems to me that there are two approaches you could take. One of these would be to work with the S/S/F configuration that was too soft and use zoning to “lift up” the pelvis area and the other would be to work with the S/M/F configuration and use an adjustable foundation to soften up the shoulder zone.
Before you try that though I would experiment with the cover because as you mentioned the S/M/F may work out for you with a cover and bedding that is a little more stretchy and “allows” your shoulders to sink in a little more deeply. It may be worth unzipping the cover in this configuration so that the top layers are a little looser and less compressed to see whether this makes a difference. It may also be worth trying to roll back the cover so you are sleeping directly on the latex (with the bedding over it) so that the cover is not a factor at all. If either of these work well then one possibility would be to replace the quilted cover with a stretch knit cover that would have less effect on the response and contouring of the latex although you would also be giving up the temperature regulation of the wool.
One other thing that would be well worth experimenting with that would also have some higher odds of success with shoulder issues is changing your pillows and head position when you sleep on your side. This can make a significant difference with shoulder pressure and may allow you to use the S/M/F configuration successfully.
If you decide to experiment with a zoned foundation then the thickness of your mattress may reduce the effect of bottom zoning so I would do some careful testing to see how much of a difference it makes for you with a similar mattress. I would encourage you to go to Sleepworks and talk with Steve there who is exceptionally knowledgeable with more “difficult” situations. I called him and he would be happy to help you but call first to make sure he is there and available because he is not often on the floor. He also suggested that the adjustable foundation would be a “last resort” and that other changes may be more effective.
If you do decide to go with zoning then some of the suggestions in post #11 here may also be worthwhile so you can do some experimenting to see how effective different zoning schemes would be before considering any more costly purchases of different layers.
I think your highest odds of success may be first to work with the cover and bedding and your pillows with the S/M/F configuration and then to work with various zoning schemes with the softer configuration.
Phoenix