Don't have time to look it up but there was a thread here about a month ago about wool toppers. Try the search engine here and see if you can find it.
I like wool but if it's too thick it CAN throw off the support of the mattress just enough that some sensitive folks might notice. I have a 2" one and though it flattens down to about 1/2", I still think it made my back hurt. I could be wrong.
But overall I love the feel of wool. And it's cool in summer, warm in winter. Maybe a 1" thick one would be the best recommendation I could personally offer.