With global warming a lot of formerly zone 5 hardy perennials now survive quite well here in the Twin Cities. The same goes for fruit trees. In fact some nurseries, such as Stark Brothers and the Arbor Day Foundation, have been adjusting their hardiness zones north since the USDA has been reluctant to do so. The Arbor Day foundation has essentially been following the Arnold Arboretum plan that Bush's USDA rejected over a decade ago.

I don't think you will need all that much protection. In fact what you suggest is probably overdoing it by quite a bit. IMO we have become Zone 5, even if some conservatives won't yet admit it.