Anne, we had two winters worthy of zone 8 in 2009 and 2010 here. My neighbor lost the top growth on all his bananas, but the roots were fine with a very deep covering of mulch. He used wood chip mulch and piles of leaves to a depth of over a foot. They all jumped right back up beautifully the next year.
Just my opinion but if you're going to grow them in ground, I'd resign myself to losing the top growth each winter, and just growing them back each year. Oh, and pray for warm winters, of course.
