I'm commenting more along the lines of potted trees. If you overwinter in pots, you won't get hard freeze. I have read data out there to show that even a hard freeze won't kill RKN, but most of my comments in this thread have been related to pot culture.
Not trying to cane a point here, just offering a thought to keep in the back of your head - with any trees, not just ones from JR. If everyone practiced this way, I honestly believe it could have a positive impact.