If you biggest concern is the back and want as thin as possible, check out the Pitaka Aramid Fiber case, I just got mine today and did a review here. Its really about as thin as it gets.
It's a CF pattern, certainly not real CF. It's a transparent CF design so it won't affect reception or charging. Can't complain for $0.35.Kawaisa,
If that true CF or a CF look? If it's real CF, has it affected your reception or NFC/wireless charging?