Hi Dcg,
This would be another preference choice. There is also more about wool toppers in post #8 here and posts #3 and #6 in this topic that may help you decide whether to add it.
I would personally make my choice based on whether your testing indicates that you prefer the mattress with or without the wool topper (keeping in mind that the wool will “firm up” somewhat over the course of the first few months).
For those that prefer the “feel” or temperature regulation of sleeping on thicker layers of wool nothing else will do and for those that prefer the “feel” of a softer foam material then it probably wouldn’t be the best choice.
Phoenix