Although they didn't have any Stayman Winesap apple trees, this turned out to be a good tip. One of the growers at their orchard wrote me back telling me that they had tried to grow some of this variety years ago and it wasn't as productive as other varieties and didn't produce very good apples.

Although I have always seen USDA zone 5 listed as within the range for this tree, that might just be included as the limit for where the tree would survive. Or perhaps it does better in other USDA zone 5 areas but doesn't tolerate the cold-warm weather swings common in the Northeast.