How can I replace an existing pergola supporting mature wisteria?

Install new posts outside existing posts. Add parallel double 2x12 to new posts making sure 2x12 is exact height of top of all wood structures but below plant. Slide 2x12 rafter on its side across from new supports ontop the parallel 2x12s mount 2x4 at end of slid in 2x12 rafter and use as fulcrum to lift plant off existing structure and turn upright keep adding 2x12s as rafters. Install if needed trellis from under with cleats. That's how we did it at my grandmothers years ago, not saying its right but it works.