I replaced the headliner in my 55.1 and it does help to have an extra set of hands. The 'floating center bar' should be attached to the front section of the headliner first. This can be done on a work bench. Exactly center the bar and possibly crimp to the front section. This headliner has to be pushed into position to line up. Take your time and you'll do a good job.
HTH BOB