Hi PrincessAndThePea,
The Soft/medium/Firm would be a fairly standard configuration that “on average” would work well. When you are outside the averages though then your own best judgement and actual sleeping experience becomes more important than any “theory”
While I share the concerns about using too much soft latex because of the alignment risk that would be involved (which can lead to back pain and discomfort) … in your case and because of your lighter weight it would be less risky and may be a good option. Only your own experience can really know for certain but given your preferences and experiences it seems that it may be the only way to go that you would be happy besides adding a soft topper on top of your mattress.
I would keep in mind that any material including latex that is that soft and thick would probably soften significantly in 10 years. While latex is the most durable foam material … Thick layers of very soft latex won’t last nearly as long as thinner layers of firmer latex. Besides concerns with alignment … this is the reason that most manufacturers are quite reluctant to go below 19 ILD or so. In your case though your lighter weight works in your favor in terms of durability.
100% natural Talalay isn’t rated to a specific ILD … only a range and I believe that Savvy Rest soft is N2 which would be in the range of 20 - 25 ILD. Scott could probably tell you which rating their soft is and it’s quite likely that it’s the same (within the variance that is common to all 100% natural Talalay).
Most soft Dunlop is firmer than the equivalent soft Talalay and I would also keep in mind that wool gets firmer as it compresses over time and probably won’t be as soft overall as soft latex. While a thin layer of wool can be good for helping with pressure points and with temperature regulation … It is not as pressure relieving as softer layers of latex or memory foam.
I would consider trying some of the Pure Latex Bliss models which have various thicknesses of 21 ILD blended talalay in the top layers and have both 2" and 3" toppers available that are in the range of 15 ILD and very very soft. This would give you a good reference point for the softest latex that is available and how it may feel over various latex combinations.
You can see the specs of the Pure latex bliss mattresses here. The Beautiful for example has 3" of 21 ILD talalay over 3" of 24 ILD and a base layer of 36 ILD. The top two layers would be similar to having 2 soft layers of talalay in your mattress and then you could even test a 2" or 3" 15 ILD topper on top of this as well (although there is always an alignment risk with this much soft latex in the comfort layers). Pure Latex Bliss has a retail store finder on their website here so you can find the retailer that is closest to you and then all you need to do is make sure they have the Beautiful on the floor and carry the toppers so you can get a sense of what very soft latex in thicker layers feels like before you exchange any layers.
Phoenix