Welcome. I've heard whispers in and around the Clemson area of South Carolina of people growing citrus and bananas outdoors, uncovered, with newly developed hardy varieties. Any experience with these fruits? Any ideas on how to give one of these hardy experiments the best chance of survival. It's around zone 7a-7b.
Yes. I cover a similar story in my book that happened in Tennessee.
The only one I can guarantee will grow is the trifoliate orange. I've seen them. However, I do think a mandarin could be grown provided it's almost completely sheltered for the first few years and still given extra care after that. Espalier against a wall, perhaps. Cold hardiness increases a lot with the age of the tree.