Personally I would advise going 1 or 2 zones colder. Since the new zone chart from the government has reclassed us as zone 6, and zone 5 plants bit the dust last winter.
We couldn’t agree more.
They moved us from 4B up into 5A, or even 5B, but that isn’t working too well.
We try for Zone 3 of 4 hardiness for any non-annuals. This past winter, though, we were down into 3B territory.