I did one roof clip, everyone should do at least one in there life
...in my limited body shop training the trick is to find something as a jig that you can lay out and duplicate on both clips tape measure wont work it has to be a solid something that wont change, I used a large Square and something else, cant recall what it was but it was hanging on the wall in the shop,
on a Camaro I would strip both tops and go for the factory joints and due whatever it takes to undue them and transfer it over, go slow and it will turn out fine its not rocket science just a PITA job.
Bud.