I am in Central MN. 70 miles NW of St Cloud. I've grown pears for years. Have Ure, Kiefer, Douglas, Luscious, and Nova. The ussurian rootstock is the best/hardiest. I find pears easy to graft compared to apple. I have a big old Ure with ussurian rootstock that keeps pushing shoots up from the roots, I dig them out, taking a piece of the root with the shoot, makes great rootstock.