I would recommend starting with the easiest way and see if you can make it work without going through a lot of extra trouble. Open the clamshell and then remove the plastic panel on the top of the area behind the rear wheel. With this panel removed you will see 3 triangulated aluminum bars converging to a single point on the rear skirt piece. Using a T-27 Torx on a 1/4" ratchet, loosen each of the 3 ends of these support bars. Do not loosen the nut/bolt where they converge. With the 3 attach points loosened, see if you can get a friend to lightly push the piece into the desired position and, if possible, get him/here to slightly over compensate. With the friend pushing (again, not too much force), secure the 3 T-27 Torx screws. This method will typically yield some results which may be enough in some cases. Otherwise, a more involved procedure may be called for.