Hi awoods,
Latex is the most durable of all the foam materials so the cover will also lose some of its initial stiffness but the latex will soften up “a little” but not a lot.
Your sleeping position is somewhat unusual (and risky) and your mattress is “in the range” that would generally be suitable for you and wouldn’t generally be too firm for most people (if anything stomach sleepers may sometimes need to use a firmer top layer) so I don’t really know what to suggest outside of “best judgement” and some trial and error based on your actual sleeping experience. If you believe your mattress is too firm then there are some suggestions in post #2 here that may be helpful but if you do decide to make any changes to your layering then the first suggestion I would make is a more extended conversation with Sleeping Organic. While it would be more risky in terms of alignment … you may find that you are an “exception” to theory that will do better with a softer Dunlop middle layer.
I think that your sleeping position may need some adjusting anyway because it is certainly risky and could cause issues in the longer term but in general I would tend to wait a minimum of two weeks (longer is better) unless it’s really not possible based on your symptoms. With your current configuration the only softer choice would be to exchange one of your deeper layers for something softer.
Yes … this is one of the suggestions in the post I linked and it would be well worth trying to see if it makes a difference. It would also be worth trying a thin pillow under your pelvis/lower abdomen to see if this helps as well.
Phoenix