Amish- I recall that you are in Zone 6, is that correct? If so, we're in the same zone and comparing notes on hardiness makes perfect sense.
I haven't been able to get the red spinach past a light frost for the greens, but have overwintered the roots under a heavy mulch successfully. That said, it's so easy to propagate and grow that it's actually better to start fresh every spring with new cuttings from plants kept indoors. I just picked the last of the curly blue kale and this last cold snap (down to 7°--sounds colder as -14° in Canadian ;-)) finished off the red mustard and fava greens. I didn't have time to put up the double low tunnels
I had originally planned.