I just wrote an article about this :)
I'm in TN as well. I don't clip but I have already started putting a light sheet on at night and once it gets low 40s/high 30s then I use heavyweights.
It depends if your going to keep eventing year round! I start to blanket when the temp gets below 60. If my horses start growing a heavier coat, I trace clip. I also have lights on a timer in the. barn to try to keep them from growing very heavy. If I am eventing and working them year round, I like to blanket with neck extensions, and of course in stalls during bad weather.