Walking in Boston, there are no stupid questions!
Stupid concepts though, like zones and more specifically, how trees change zones inside pots.
Remember this is something that you will be doing probably forever. Every year that 5/6 tree is going to get a little better and your time into it greater. It dying will hurt more every next year too. So going about it, well, at all may be a bad idea, but half assed certainly is.
I'd ignore zones all together and see if that works. If not, decide wether to setup a legit area of moderate expense to ensure they never die. Otherwise you're setting yourself up for a sad day.
I'm convinced it's not the cold, but the more rapid onset of it that kills lesser zoned trees. They just don't have the time to prepare. Setting them on the ground to connect to the much network can help this IMO.
Next up for debunking....chill hours. Another stupid concept.
Sorce