It's going to be very hard finding anything decent tasting that's hardy to zone 7b, even with passive light protection.
If it's not killed back the first winter, it will eventually get killed back when a cold winter comes along after a couple of years.
If you're on the border of zone 8a/7b, that may be a different story.
You may try citrumelo (Duncan is supposed to be better tasting than Swingle).
Citrumelos and citrandarins tend to be the hardiest hybrids I am aware of. A kumquat-trifoliate hybrid may be even a little bit hardier.
US 852 (citrandarin) may be the hardiest one with half-decent taste that could survive well in zone 7. (Keep in mind that doesn't mean great tasting, just edible, with only some slight off flavor)
Stan was shipping out boxes of the fruit last year when they were in season. Full of seeds.
Nat Bradford also told me he had luck with Taiwanica lemon (border of 8a/7b South Carolina). Not at all good tasting, but it doesn't have poncirus in it.
Further north it just gets more difficult because the citrus doesn't have time enough to grow to recover from damage, and the cold drops are typically longer in duration.
