Hi Parran,
I was looking for the ILD range of their Dunlop layers because they don’t mention them on their site (they don’t even mention there is a choice). Different manufacturers have very different ideas of what “medium firm” may be and knowing the ILD ranges of their Dunlop would be helpful.
I also wanted to make sure that the comfort layer you had was the 19 - 21 ILD they list as one of their options just to make sure that we were on the same page.
It would also help to know what type of foundation your mattress is on so that it can be eliminated as a possible cause of any issues.
This would vary with each person and is not really possible for anyone else to know except through your own experience. I personally think that with your lighter weight that the 3" layer you have on top would be enough to shield you from the firmness of a firmer support layer but like all things that are based on specs it is only speculation because there is no formula to be able to know what any person may feel on a mattress.
If I had to guess at the most probable layering for you it would either be 3" of soft over a firmer support core or 2" of soft over a somewhat softer support core (probably similar to what you have). Both would reduce the amount the heavier parts of your body would sink in and probably lead to better alignment but testing similar layering locally would be very helpful.
I’d be happy to tell you the most probable effects of each change (and I’ve already listed most of them) but the only accurate way to know for sure would be testing in person either on similar mattresses that were available locally or through your personal experience on the new layering. There are too many variables between people to know for certain how anyone will feel on a particular layering combination except through using “averages” (and based on your descriptions you are probably not in an average range) and what your experience on one specific layering “points to” in terms of any changes that may be most desirable in the next one. This is just part of the nature and risk of an online purchase where averages may not always apply to any specific person. The best idea is always to go slowly and try to think through exactly what you are wanting to accomplish with each change, to make sure you have tested each combination for long enough to make sure you are seeing consistent patterns instead of just a few nights experience which may be an anomaly, and to narrow down as much as possible the most likely cause of any “symptoms” you are experiencing (by describing them as accurately and in as much detail as possible).
I can also tell you that with your multiple sleeping positions and lighter weight that thinner comfort layers that use softer materials are less risky (and leave more room for making fine tuning adjustments with mattress pads and/or toppers) than thicker layers of the same soft material.
Before you make this decision it may be worthwhile knowing what the local alternatives are or at least using them to help establish a reference pont. There are several choices in the Baltimore area that would at least let you test latex mattresses of various types that could be very helpful. They are listed in post #2 here.
If I’m not mistaken they cap the fee of return shipping at $99 and will probably make the arrangements to have it picked up by the company they prefer. Many companies that do this will send you prepaid shipping labels. They should also give you suggestions about the most effective way to pack it (putting it in a plastic bag and then vacuuming out the air can help to shrink it).
So I would start with confirming the ILD ranges of their base layers and that combined with some local testing may help you decide on what the best next step may be.
Phoenix