I've seen your post for a while. Since you haven't gotten another answer I'll share my opinion. I lived on the south side of Jax for several years and had a Satsuma I planted which obviously was a young tree. I only covered it when we had the snow/sleet storm in the early 90's. I never had problems with the fruit. My tree was actually a novelty in the neighborhood. Being from central Florida I couldn't imagine not having any citrus. I have commercial groves around me now and if it is below 32 for I believe 4 or more hours they harvest. The Satsuma tree can take more cold than the others which is why I chose that tree. But I think all citrus fruit is going to freeze under the same conditions. I would definitely harvest for a freeze lasting 8 hours or more.