Last October, we had an early snowfall that coated an old apple tree, which, in turn, fell upon my Magnolia (Magnolia acuminata 'Butterflies') and broke the central leader branch. I left the tree to grow and bloom, to be certain that it survived the damage. It bloomed reliably, but now has unpleasing shape, with long arching side limbs. I would like to prune it to create a more upright shape, but am uncertain if this is wise, or how to go about it. Any suggestions?