A hard pruning at this point in the year will result in a lot of soft new growth that may or may not survive the winter. In Z7 in a protected location near the house all may be well, especially if you protect the new growth with a burlap screen or other device to shield it from winter sun and wind. Even if the late growth is winter killed, you'll be pretty much back where you started next spring. Another pruning back into green wood at that time will give you a flush of new growth for next summer.