We're training the vines up to a 5 foot fruit wire in 2010. So far it appears the winter cold is not as much as an issue as early fall frost. So by raising the wire from 22 inches to 5 feet we wont have the bennefit of the snow cover in the winter however, the fruit wire at this height offers a few degrees of frost protection.
Good research on this
We're also looking at bird netting as we are going to need it but there are some on the market that provide a degree or two of frost protection. Were going to try this out and see if it works.
We're not really worried about the frost because the varieties we've chosen appear to be early enough for our site that it should not matter. Having said that, being able to let the grapes hang a week or two could do wonders for the juice chemistry perhaps increasing the brix 1 or 2 points while dropping the acid to levels if it happens to be a bit high - we'll see.